Cycling a New Aquaponics System. Quick Guide.

How to Cycle a new Aquaponics System.
Have your system built and the water circulating, the auto siphons are functioning and adjusted well. If you have decided to use a timer system for flood and drain, then your timed cycles should be functioning well. You have run the system long enough for the water to be clearing.  The water can be a bit dirty from loose dust on the clay pebbles or gravel, but it should start to clear after a few days.

Barra in a basket

Small Barramundi contained in a plastic laundry basket within the fish tank. This makes it easy to take the fish out and treat them in a salt bath if necessary.

Small Barramundi contained in a plastic laundry basket within the fish tank.  This makes it easy to take the fish out and treat them in a salt bath if necessary.

Adjust the pH to just below pH 7. Adjust using pool acid to bring pH down or hydrated lime to adjust pH up. Get some plants in there right away.  The plants will soon tell you if there is not enough nutrients.  Use some Maxicrop or Seasol seaweed extract to provide some nutrient for the plants.  It will not harm the fish once you have them in the system.
There are very small amounts of ammonia in these products, so the process of building a suitable colony of beneficial bacteria will be slow, but it is a very safe and gentle way of cycling your system. Be patient.  These are natural processes and they take time. If you feel you must  speed the process, then, in addition to the seaweed extract, add a VERY SMALL amount of Urea.  No more than 1 teaspoon per 1000 litres of water.
If you can obtain some pure ammonia then use that in preference to Urea.  Once again, very a small amount like 1 tablespoon per 1000 litres (250 gallons). I stress that my preference is not to use Urea.  It can be vicious and cause lots of problems if overused.

The beneficial bacteria are naturally occurring, and they will begin to multiply once there is ammonia present. One option t ensure you have a good number of the beneficial bacteria present is to add some water , 3 or 4 liters (1 gallon) from a disease free freshwater aquarium, or a friends Aquaponics system.  The beneficial bacteria will be in this water and will take up residence in your new system and begin to multiply and use/process the ammonia. After your system has been running for about two weeks and everything is going nicely…..add the fish of your choice.

Stock lightly for your first batch of fish. Don’t be tempted to have a lot of fish in the beginning. Remember , loads of aeration and a backup system. Conduct your usual tests for Ammonia, Nitrites,  Nitrates at the following frequency. Daily for pH and Ammonia. Every second day for Nitrites. When the Nitrites appear you will know that the beneficial bacteria are on the increase. A short period of time after that Nitrates should start to appear. Test for Nitrates every second day until you see them appearing.  Once you see Nitrates you know that your system has cycled. All the while test for Ammonia.  If it goes beyond 1.0 mg/L then carry out a one-third water change.
The good thing about having the plants in is they are capable of taking up some of the ammonia.  Once the system has completed the "cycling" process tests for ammonia should reveal very small amounts or even none at all on occasion. All the while test pH.  Try to keep it just below pH 7.   It is not uncommon to observe swings in pH during this early period.   Don’t panic and start chasing the pH.   Only adjust when you see a firm pattern developing, for example, if it stays at say, 8.0 for 3 days, adjust gradually down using pool acid or similar…….be gentle, adjust in small increments, until you get it steady just below pH 7.

Once your system is up and running and everything is just fine, if you want to introduce more new fish always quarantine them in a salt bath for a week before putting them into your main system.  Don’t risk bringing sick or infected fish into your working Aquaponics system.
Happy Aquaponics Murray.

C.H.O.P Aquaponics Operating System.

CHOP System.

The CHOP system is an acronym for   “Constant Height One Pump”. This is the most efficient way to run an Aquaponics system.

The basic principal is to use the force of gravity to assist us where possible. This brings high efficiency in electric power consumption and plumbing design.

The CHOP system is also better for the health and wellbeing of the fish, as it means there is more water in circulation that brings stability in both temperature and pH.  Because the fish tank is always full of water, the fish are safe if something goes wrong with plumbing or pump.  The auto siphon system is an automatic way to flood and drain the media beds without the need to employ float switches or timers.  The system is lower maintenance than older system designs that required float switches, timers and a second pump.

CHOP or Constant Height One Pump has been adopted by Aquaponics enthusiasts around the world and its popularity has demonstrated the methodology’s effectiveness.  The other variant CHIFT PIST (Constant Height In Fish Tank. Pump In Sump Tank) runs in a similar way.  In fact CHOP as an acronym was coined because the acronym CHIFT PIST was thought to be a little clumsy and crude.

Constant height in the fish tank is important in that we want to have a system design that ensure that the fish tank cannot be run or pumped dry should something go wrong, such as a pipe failure somewhere in the system.  If something goes wrong and the sump is pumped dry and or the media beds run dry, it is not desirable but it is not a disaster as would be the case if the fish tank is pumped or drained dry.

One pump is important from an economical operation point of view. So, our plumbing design is such that all the water can be moved around to all parts, in the volumes we require for each section of the system, by the one pump.

The pump resides in the sump. All pumping is done from here. I like to call the sump “Grand Central Station”. It is the central meeting point of all the water flow in the system. The water is pumped from the sump to the fish tank, and from the fish tank the water runs by gravity to the media beds.  The auto siphon or timer allows the bed to fill then drain back down to the sump.   In this way there is only one regulated flow around the entire system and that flow rate is dictated by the auto siphon/s.

CHOP system methodology allows us to use the absolute minimum of power to move the water around.  Aquaponics systems are perfectly natural systems except we have to move the water, and we can only do that with pumps of some sort or another.  So, over a period of time we have strived to get our pump size down and enjoy a very minimum of power usage.  In CHOP systems the water flow in one direction is done by gravity and in the other direction it is removed from the sumps back to the fish tank by the most efficient pump possible.

Originally, our systems had two pumps in them all the time, one was required to move the water out from the fish tank and one to move it back and we quickly discovered that that was just a waste of energy. This is another advantage of the CHOP system.

CHOP 2 System.

Chop #2 is a further and much improved variant to the standard CHOP methodology.  We noticed a problem with water levels whilst working on a small commercial CHOP system we were commissioning.  Running the feed water from the fish tank via a filter then on to be distributed to each media bed by gravity flow was problematic.  If all the beds were not precisely level with each other the lower bed/s would receive more water than the others. This could be regulated with valves on each bed water inlet.  This works fine on small systems, but the larger the system the larger the pipe work needs to be in order to accommodate sufficient water flow by gravity. Evenly distributing water by gravity to six beds that together were 30 meters (98’) long was near impossible.

We needed to refine the process for our client, so we came up with a solution that has been working well for several years, and now on many thousands of home systems and a good number of commercial systems. Pumping the water to the media beds, positive pressure delivery instead of gravity delivery.  It is relatively easy to ensure even distribution to each bed and also to the most distant bed delivering the water by positive pumped, or header tank pressure. The system water is delivered to all points under pressure, either by pump or from a header tank. The pump is located in the common collection and distribution point; the sump.  All the water arrives from the various parts of the Aquaponics system into the sump, all water leaves from the sump to the various parts of the Aquaponics system.

Water is delivered, as necessary, in various loops to the media beds, the raft beds, the fish tank and if included, to the mechanical filter.  The water is collected from each loop or system segment back to the sump.  The water is delivered to each loop or system segment from the sump under pressure either by pump or header tank.  The water flow is regulated to each part of the overall system by the use of a simple valve or tap.  Very accurate flows can therefore be achieved.  CHOP 2 allows the operation of each element of our Aquaponics system at its ideal flow rate. This multi loop arrangement allows much more flexibility in plumbing design and precise flow control through the various elements of the overall Aquaponics system.

Happy Aquaponics.

 

 

Fish Problems & Diseases.

Fish Problems & Diseases.

Our Aquaponics fish can be subjected to various difficulties that will cause them to be in a less-than-ideal situation leading to sickness and death. Most fish problems are human induced.

There are not that many diseases your Aquaponics fish can contract.  If you buy your fingerlings from a hatchery that can issue a health certificate for the fish, then buy from that hatchery.  It is well worth the little extra it may cost to buy fingerlings from a certified source. That way you start off well and provided you have good water quality and loads of aeration, there is a very good chance that your fish will not get sick.

Stress.  Fish can easily become stresses by a number of factors. Do everything to keep your fish happy and feeling safe.  Stress is detrimental to fish health just as it is for humans and any other animal. Prolonged stress sets the fish up for bad health outcomes.
Stress is identified by,

  • Fish are skittish and easily disturbed.
  • Gasping at the surface.
  • Strange swimming patterns.
  • Loss of interest in feeding.

Stress can be caused by,

  • Poor water quality, pH , excessive nitrate, nitrite, ammonia.
  • Excess of dissolved solids.
  • Low dissolved oxygen. Power outages. Pump failure.
  • Bullying by other fish.
  • Excessive handling by humans.
  • ICH. Sometimes named “white spot”. The  scientific name isIchthyophthirius multifilis.   

Treat and avoid stress by,

  • Cleaning up the water quality in your system. This may require the cleaning of the filter if you have one fitted to your system.
  • Fit a filter, a simple settlement tank or swirl filter will make a world of difference if the system has visible solids in the water column.
  • Feed at the correct rate. Overfeeding brings on a raft of difficulties.
  • Ensure the system is within parameters for pH, ammonia, nitrite and nitrate.  (see our training material for recommended parameters)
  • Add extra, additional aeration from a different source. There cannot be too much dissolved oxygen in the water.
  • If there is an identifiable bully in the tank, remove the offending fish. (maybe to the dinner plate)
  • Reduce the frequency of opening and closing the lid on the tank. Minimise scooping fish out to inspect them. Only do this if really necessary.
  • Once a disease problem is identified, treat early rather than late.

Next newsletter we will deal with another common difficulty for our Aquaponics Fish.
If you can, attend one of my training courses to get detailed information on how to have a very successful Aquaponics system.
Regards Murray.
------------------------------

Grow Beds in Home Aquaponics Systems.

The GROW BED is the multi function centre of the Home Aquaponics System.

The Grow Bed performs several very important tasks, and if we were to try and describe those functions in a simple way, one suitable description would be, it is a Bio-Filter in which we grow plants.
A very happy and combination of duties. It is extremely convenient for our purposes, because as a Bio-Filter it collects and processes the ammonia and solid waste from the fish and returns the water to the fish tank clean, and by the growing of plants in the Bio-Filter (Grow Bed) we use up the nutrients and nitrates produced in the Bio-Filter (Grow Bed) producing excellent quality fresh veggies for our table.

Because the Grow Bed is such an important part of our total Aquaponics System we need to put some careful thought into it's design. Materials used, dimensions and location relative to the fish tank are all considerations.
We strongly recommend the use of 300mm (one foot) deep grow beds in your Aquaponics system. Beds with less depth and therefore volume, will also work, but not nearly as well.

The Grow Bed needs to be of such a length and breadth to provide sufficient surface area for the plants and together with depth provide sufficient total volume to be an effective Bio Filter.
Overall volume of a grow bed is an important factor. The more volume the total system has, the more stability in the system , particularly in temperature and pH.

This stability has obvious flow on benefits for the health of the system inhabitants.

Fish, plants, worms, beneficial bacteria and microbes all function better in a stable environment.

In taking the decision to operate an Aquaponics system, we are desirous of producing the very best, healthy, nutrient rich and economical, plant and protein, for our family.
Aquaponics can deliver such produce by making use of natures wonderful interactive systems of worms, microbes and bacterium in a naturally balanced environment. It all works to its optimum when we provide it the best environment possible.

300mm (or more) deep grow beds will deliver optimum plant growth and health. They will provide optimum environment for the processing and delivery of nutrients to the plants, and the processing conversion of the ammonia given off by the fish, to nitrates.

In forming this opinion we have relied, not only on our own actual, very significant practical experience, but also on the experience of dozens of very experienced AP practitioners in Australia and around the world. Many of these people have accumulated a large body of experience in the use of 300mm deep (or deeper) grow beds as part of a well constructed Aquaponics system.

All of these people report exceptional healthy plant and fish growth using systems based on the 300mm deep grow bed principle. There is now a large body of actual evidence that strongly shows that this is a good working principle/method.

We have manufactured and delivered many hundreds of complete AP kits based on the 300mm deep grow bed, and hundreds of 300mm deep grow beds to persons who are constructing DIY Aquaponics systems.

Flood and Drain:
Together with a 300mm (one foot) grow bed depth, we strongly recommend using flood and drain cycle and 20mm drainage gravel or similar in your grow beds.
Flood and drain water movement system ensures the even distribution of water, nutrients and air (oxygen) throughout the system. This provides multiple benefits.
By the use of this method, dry or nutrient and oxygen areas are prevented from forming in the grow bed.

Nothing less than 20mm (3/4”) gravel should be used. This common gravel, by the way it rests together provides easy passage of water, solids, and worms throughout the bed.

Often folk cannot envisage plants growing in such a coarse media and they choose a finer media such as 5 or 10mm. This sized media will impede the action of the worms, the easy movement of solids and nutrients, and the Grow Bed will quickly suffer from partial or complete blockages.
Listed below are some of the reasons why 300mm or deeper grow beds are good....very, very good and highly recommended to deliver excellent results in your Aquaponics System.

Room for plant roots to develop and grow. 
Some plant types such as lettuce do not require much depth (or nutrient) to grow successfully, but other garden plants such as tomato and corn, just to name two more common ones, do need depth space to put down good root systems. A given grow bed will have a variety of plants grown in it, so a grow bed depth bed depth that will accommodate a wide range of plant requirements is the way to go.

Depth and volume to process solid waste.

Solids passed by the fish, old roots, and other solid material is processed in the grow beds by those little wonder worms. Without going into detail here about the role of worms in AP, sufficient to say that the worms reduce solid waste by 60% or more and by their work and the action of flood and drain distribute the released minerals and nutrients throughout the grow bed/s.   300mm ( 1') deep grow beds filled with 20mm (3/4") drainage gravel with a good population of resident worms deliver an amazing plant growing habitat. (Not to mention excellent filtration for the fish tank.)

Bed Zones are established. (See illustration below)

Surface or dry zone. --- # 1. The first 50mm is the light penetration and dry zone. Evaporation from the bed is minimised by the existence of a dry zone. Water waste minimisation is a very important principle in Aquaponics systems.

This dry zone also protects the plant base against collar rot. Additionally, by ensuring that this zone is kept dry, algae is prevented from forming on the surface of the grow bed media. Because this dry zone is present, moisture related plant diseases such as powdery mildew are minimised.

Root zone. --- # 2.  Most root growth and plant activity will occur in the next zone of approximately 150 - 200mm –in this zone, during the drain part of the flood and drain cycle, the water drains away completely, allowing for excellent and very efficient delivery of oxygen rich air to the roots, beneficial bacteria, soil microbes, and the resident earth/composting worms.

During the flood part of the cycle, the incoming water distributes moisture, nutrients and incoming solid fish waste particles throughout the growing zone. The worm population does most of its very important work in this zone, breaking down and reducing solid matter and thereby releasing nutrients and minerals to the system. ?Worm Tea”, as it is commonly known, will be evenly mixed and distributed during each flood and drain cycle. “Worm Tea” and the fish are entirely compatible, No possible harm can come to the fish by the distribution of this wonderful nutrient material throughout the Aquaponics System.

Solid collection and Mineralisation Zone - # 3.
This is the bottom 50plus mm of the grow bed.   In this zone fish waste solids and worm castings are finally collected.

The solid material has been reduced by up to 60% by volume, by the action of the resident garden/composting worms, and microbial action.
During each flood and drain cycle, what is left of the solids perkolates down into this zone
Further and final mineralisation occurs in this area via bacterial and earth worm activity. Due to the excellent action of the flood and drain cycle, this bottom area is kept “fresh” and vital by the excellent delivery of oxygen rich water during the flood cycle.

Some water storage occurs in this bottom zone.
Should the flood and drain cycle stop for any reason, such as a mains power outage, the bed will slowly drain down and leave approx 50mm of water at the bottom of the grow bed.
The stored water provides a safety buffer in the event of power outage or pump failure... This stored water ensures that the plants will survive for very long periods without water flow.

This means that we can simplify our safety backup system to circulate only the water in the fish tank, by the use of low wattage water pumps and/or aerators.  We can safely operate the system in backup mode (no main power supply) for very long periods of time–simply using an average size car battery as a power source.

This inbuilt water storage zone will supply the plants with water and nutrient should we need to isolate the fish tank for maintenance purposes, or treatment of the fish.

____________________________________________________________________________________________

 

Salt In An Aquaponics System.


Sea salt harvest in France.

Salt in your Aquaponics system
The addition of small concentrations of salt to your Aquaponics system is a practice that you may read about as you surf the net gathering information. As with all things, there are advantages and disadvantages.

Advantages
Salt is a wonderful, non “chemical” way to treat diseases and bacterial infections in fish. It is also a good “tonic” in the sense that it helps the mucous coating the fish has over its body. This coating is the fish's main defence against disease attack. Fish gill health is also enhanced by salt by helping ward off or treat attacks by parasites.

The advantage of this procedure is said to be disease prevention. Salt helps to guard fish against fungal diseases such as ‘ich’ and some bacterial problems.

Some operators of home based Aquaponics systems run low concentrations of salt in their Aquaponics systems as a tonic, or disease preventer for the fish.

Disadvantages.
Salt interferes with plant growth/health.
In Aquaponics systems water from the fish tank is used to grow vegetables and other plants. In a recirculating AP system or an open ended AP system any added salt will reach the plants.

Most food plants have very adverse reactions to salt. Some plants such as strawberries will die if there is any salt at all present in the water  However, added salt in carefully managed low concentrations, can be used and acceptable plant growth, for most food plants, is still achieved.

How much salt to add.
The salt is added at the rate of between 1 and 2 ppt.
Concentrations higher than this can be used depending on the plant types being grown, but as a general overall rule 2ppt is as high as is practical for home based systems growing multiple crop varieties.
There is a need to have an accurate way to measure the salt concentration because the concentration will change as the system is operated normally. Some variables are, water is taken up by the plants, evaporation, water top ups, losses due to plumbing leaks and so on. Any of these or a combination of factors can all change the overall concentration of salt in the system.

A useful way to keep track of the salt concentration in the system is to use a low cost refractometer. Basic but very useful refractometers can be obtained for as low as twenty four dollars, or up to several hundred dollars for the more sophisticated digital instruments. The low cost refractometers are very satisfactory for use in home based systems.

What type of "salt" can be used.
Ideally a pure sea salt should be used. This can be difficult to obtain in quantities that may be needed for Aquaponics purposes.   The least expensive readily available salt is Swimming Pool Salt. Make sure you read the label to see if there are any additives, but there usually is not.
Table salt is unsuitable because of the addition of "anti caking" agents and the like rendering it unsuitable to be used for fish.

Other ways to use salt.
Many Aquaponics practitioners prefer NOT to run salt in their AP systems, but rather keep the use of salt as a treatment method if and when a disease problem arises.
It should be pointed out that in a well managed home based Aquaponics system, disease problems for the fish are almost nonexistent.

Diseases such as “ich” ( a gill resident parasite) usually are brought in when new fish are obtained from the hatchery or other source. Bacterial infections usually only appear when the fish are stressed for one reason or another.  Introduced problems like “ich” are well managed by quarantining any new fish.
This is the time to use salt to great advantage.
Every Aquaponics installation should have a “hospital/quarantine” tank. This tank will not need to be all that large, say, two or three hundred litres (75 gallons approx). Ideally it should have a good quality canister filter attached, but any well constructed filter system like a trickling bio filter can be used. Plenty of dissolved oxygen is delivered to the hospital tank by the return water from the filter and splashing on and disturbing the tank water surface and an additional air bubbler.

Use a higher concentration of salt in the hospital tank. Perhaps even up to 1 or 2 parts per thousand if the fish are to be left in the hospital tank for several days or even weeks.

Short intense treatments can be carried out using concentrations of up to 10 parts per thousand.
Caution needs to be exercised here because not all fresh water fish species will tolerate these high salt concentrations. Check with your local fisheries department for information regarding your particular species.
I have used 10 parts per thousand on Jade Perch, Silver Perch, Sleepy Cod and Barramundi with good success. High concentrations like this are only used for short periods of time, say 2 to 6 hours. The fish are then returned to a much lower concentration for the rest of their stay in the hospital tank.

Another method used with good success is to dunk new fish in a concentraton of 10 parts per thousand for 3 to 5 hours, then place into their regular tank. This is done 3 or 4 times two weeks apart. The fish are kept in a floating basket during this time to make it very easy to treat them. They are just lifted out of the regular tank and into the salt tank . When the 3 to 5 hour treatment is finished, just lift them back to their regular tank.

_____________________________________________________________________________________________________

 

Cycling a New System Using UREA

The use of UREA as a method of cycling a system should be done with caution. Steady as she goes.
Use very small amounts. Some members have got into a real mess by getting heavy handed with the UREA.
If you must use UREA in your new Aquaponics system...just once only....half a teaspoon...then a CAP full of Seasol daily after that.  (Seasol is a seaweed extract commonly available in plant nursery shops)
Plant your plants immediately.
After about two weeks...get the fish.
Assuming you are getting fingerlings..not large fish.

Plants will use directly some of the ammonia produced by the fish, so it is good insurance for the fish to have plants into the system right from day one. The plants will do very well on the Seasol. There is very little ammonia producing elements in Seasol, but there is enough there to get the good bacteria going.
As the plants grow they are more and more capable of directly taking up ammonia produced by the fish.

Be patient, in the dead of winter it could take 4 to 6 weeks to get a nitrate reading. Don't be tempted to "give it a bit more" to try and hurry everything along.

To convert the UREA to a usable form of Ammonia an enzyme contained within a specific bacteria is needed, (urease) that is found in soil but rarely found in a new aquaponics system. This is one of the reasons why people get varying results when attempting to cycle with urea.
It also explains why repeated use of urea in regular dirt gardens (and new aquaponic systems) has ever diminishing results, and why leaf burn occurs because the enzyme needed to convert is either not available or not available in sufficiency quantities.

Urease is an enzyme that catalyzes the conversion of urea to ammonia and carbon dioxide. Certain bacteria that convert urea to ammonia as part of the nitrogen cycle contain this enzyme. 

The conversion of urea and water into ammonia and carbon dioxide, one of many biochemical reactions catalyzed by enzymes.
Ammonia changes it's state when passing through Ph 7 making it either toxic or less toxic to fish.

For this reason it is very important to keep control of the pH in a new system.  Ammonia is much more toxic to fish at pH 7 or above.

Much more attention should be paid to pH management than anything else.  If your system is above 7 pH then even small amounts of ammonia will be a threat to your fish.

So when cycling your system make sure you test for pH daily and take steps to get it to 7 or just below before you introduce your fish to your new system.
_____________________________________

pH , Nitrite and Nitrate – Ideal levels.

pH will tend to drift down over time in a well balanced system and will need to be buffered up from time to time.
In a new system that is in the process of being cycled it is not uncommon to experience swings in pH.  The type of media used can have a bearing on pH.   For example, some gravels can be high in natural lime or similar akaline elements.  This situation could make it difficult or even impossible to keep the pH at 7.0 or just below 7.0

In a system that has completed cycling, Ammonia should be very low, only barely detectable, sometimes not detectable at all.

If the good bacteria are present and in sufficent concentrations, and there is sufficent water movement, the Ammonia will be processed very quickly.

Nitrite will be seen when the system is part way through the cycling process and not be seen in a balanced system.  As the system is cycling Ammonia will first be detected, several days later Nitrite will be detected.  Then finally Nitrates will be seen.

Nitrates can be moderate to high without harming the fish. Nitrates should not be high permanently. If they are consistently high, plant more grow beds out to use up the nitrates, or reduce feeding of the fish.
If Nitrates are very high over a long period of time fish health will be diminished.

______________________________________________________________

Fish Food – How Much Do I Give Them Per Feed.

Fish Food—Feeding your fish using commercially available sinking or floating pellets.

The fish food we supply is suitable for all Australian Natives.
The fish food has NO land animal content.
Be careful not to over feed your fish. This results in wasted food and fish food lying around on the bottom of the tank can cause an increase in the ammonia levels in the tank.
There are formulas that can be used to calculate exactly how much food to give your fish per day.  The formulas are grams of food per grams of fish weight.  To exercise the formula correctly requires that a number of fish be caught and weighed on a regular basis, establish an average fish weight, then  calculate the correct amount to feed.

For domestic home based systems this is impractical, so a "by observation" method is better employed.
Observe carefully as the fish take feed. Any food not taken up within 20 minutes or so is too much. Regulate the amount of food given to the fish at each feed time by observation. If your new fish are very small, use a coffee grinder or similar to break down some of these pellets into finer particles for the new small fish to consume.
Gradually increase the size over the first weeks until they are feeding on the full size pellet. New fish will not usually feed much in the first few days., so be patient with them giving them small feeds until you see evidence that they are feeding. If you disturb the fish this may put the fish off their food. Changes in temperature and other conditions may also put the fish off feeding.

It is a common problem, overfeeding the fish...so exercise caution.
Australian natives, almost withour exception can go for extended periods of time without being fed.   If you need to go away for a week, it is better to purchase an auto fish feeder device (available from most aquarium shops) to give a regulated amount of feed per day.   If you cannot do that, it is better not to feed them rather than get a neighbour to take care of the task.   Most inexperienced but well meaning folk will overfeed your fish, resulting in an excesses of rotting fish food in the tank which will cause an ammonia spike and the possibility of fish deaths.

_________________________________________________________________________________

EC = Electrical Conductivity

Electrical Conductivity is a good way to measure the nutrient concentration in your Aquaponics System. That is a measure of the water borne nutrients available to the plants. It should be noted that it is not a complete measurement of nutrient in an Aquaponics System, as there are organic nutrients present that an EC meter will not measure. However, over time, the overall measurement is a very useful one.

Conductivity helps you to determine if you are getting the balance between the fish food given or placed in the system, to plant growth.

The range of Electrical Conductivity can be as low as 0.2 and as high as 2.0
In my newest system the reading is 0.5 and is increasing weekly as the system matures and the fish grow.

In another of my Aquaponics Systems that has 126 Sleepy Cod, the EC reading is 1.8. This is a very mature system. The high reading and the maturity of the system indicates to me that I can easily add another grow bed or two.

The same number of fish and feeding regime will easily support more grow beds and produce more vegetables. The EC reading would gradually drift down and find a new level after the grow beds are added and planted out.

Keep in mind that not all the nutrients present in an Aquaponics System will be measured by an EC meter. As an example of that, in the newer system (Patio Duo) that has an EC reading of 0.5, that system is enjoying good plant growth. This is evidence that there are organic nutrients present in an Aquaponics System. If we were relying solely on added nutrients such as commonly available hydroponic nutrients, plants just would not be doing very well at all with an EC reading of 0.5
Obviously this Aquaponics System will continue to improve over time and be even better.

You should not attempt to drastically correct low EC readings in your Aquaponics System by adding non organic nutrients. Slow and steady is the way. A good variety of fish food is required for the system to be well balanced in nutrients. Make sure your fish are happy and the rest will take care of itself.

As your system matures, if your EC readings are remaining low, you possibly have too many plants or two few fish. Aquaponics is all about balance.

What to feed your fish is the subject of another discussion.

Overall, a good quality EC meter is a valuable tool in maintaining a good Aquaponics system.

EC Truncheon

EC Truncheon

Sales information can be found here.Click here

 

"EC Meter. Very easy to use and provides useful information."
____________________________________________________

Can I Use Galvanised Tanks for Grow beds ?

Galvanised tanks are coated with zinc. Over time the zinc coating oxadises and is leached into the water body, and zinc is well known to cause problems for fish.

The use of Galvanised tanks goes against common accepted knowledge and also a lot of research that can be easily accessed.
The way in which zinc affects fish is death by tissue hypoxia.
Below is some exerpts from a scientific jounal that should prove to be interesting on the subject.

Acute zinc toxicity to rainbow trout (Salmo gairdneri): confirmation of the hypothesis that death is related to tissue hypoxia Burton, DT | Jones, AH | Cairns, J
Journal of the Fisheries Research Board of Canada [J. Fish. Res. Bd. Can.]. Vol. 29, no. 10, pp. 1463-1466. 1972. 

"Acute heavy metal toxicity to fish has been attributed to the coagulation or precipitation of mucus on the gills and/or to cytological damage to the gills. The physiological mechanism of death by either of the above causes is related to a breakdown in gas exchange at the gills. This study of acute zinc toxicity to rainbow trout (Salmo gairdneri) supports an earlier hypothesis that modification of the gas exchange process at the gills creates hypoxia at the tissue level. Tissue hypoxia appears to be a major physiological change preceding death once the gas exchange process at the gills is no longer sufficient to supply the oxygen requirements of the fish."

Hypoxia is a condition of oxygen reduction in humans and animals. As an example, mountain climbers can suffer hypoxia when climbing at altitude, which causes initially disorientation followed by nausea then ultimately death.

Research shows that as little as 35 thousandths of a thousandth part can be detrimental to fish.
So the fish will die exhibiting the same symptoms as if there is lack of dissolved oxygen in the water.
I would suggest that some folk have gotten away with using old galvanised tanks to date, because they have been raising Tilapia which are well known to be able to tolerate poor water quality and low DO levels.

Trout or Barramundi are at the other end of water quality needs and would quickly succumb to zinc poisoning if placed in a system that had galvanised tanks or grow beds..