Mineral and Nutrient Supplements in Aquaponics Systems.

The question is often asked if there is a need to add mineral and nutrient supplements to Aquaponics systems. The answer is both yes and no.

In the very beginning, I advocate the use of a seaweed extract such as Seasol or Maxicrop or Kelp and Fish Emulsion as an initial boost for a new system. It gives the new system something to work on and acts as a tonic for the new system aiding in the establishment of the beneficial bacteria..
A new Aquaponics system needs time to develop all the bacteria and microbes that will convert and release the necessary nutrients for good plant growth.

Seaweed Extract

Fish and Kelp Concentrate

Aquaponics systems closely mimic nature in the way they handle and provide nutrients for the plants. Eventually there is a myriad of bacteria and other microbes that do their job, just as they should in a mature Aquaponics system.

The job of the two main beneficial bacteria in converting the ammonia produced by the fish to nitrates is very obvious. They are established in a new Aquaponics system usually within a few weeks. It takes time for all the other natural processes to develop and establish.

This is the amazing thing about Aquaponics . The way it becomes so balanced and complete.  Aquaponics is an ECO system.

I also advocate the use of "worm extract" or "worm juice" as it is sometimes known. This is done to help “kick start’ the mineral and trace element build up in your new system. Worm juice is not always available to you so the Kelp and Fish Emulsion is a good standby to get your new system up and running.
It should be applied at the rate of a CAP full a day.  This can be continued right up to and past when you add the new fish to your Aquaponics system.  Our Fish and Kelp Concentrate will not harm the fish.  Natural organic mineral supplements work slowly and are not like chemically derived fertilisers.

Fish and Kelp Concentrate, or Seasol or Maxicrop can be applied once every three or four months to assist in a balanced mineral load in the system, and as a tonic for the Aquaponics system.

It is a good idea to add it at the grow bed water entry point and allow it to peculate down through the grow media and make it's way around the system carried by the water.

You may find it a good idea to add a half a teaspoon of Chelated Iron to one of the grow beds once a month. Iron deficiency is often encountered in new systems. This is most often a symptom of “Nutrient Lock Out” caused by pH above 7. As pH stays above 7 nutrients are locked up and are not available to the plants even though they may actually be in the system.

Aquaponics systems run best at pH 6.2 to 7.0.

If adding Iron, just use a little water to wash the Iron down in amongst the grow bed media. The Chelated iron can also be added straight down into the water beside the auto siphon device.
This way the iron will be dispersed more slowly around the bed/s. Even though it is added to just one bed, it will find its way around through the entire system.

Potassium and Calcium are also needed in Aquaponics systems. If feeding your fish on commercially available pellets these two elements are often in short supply in your aquaponics system.

These two elements are easily supplied as part of pH control / adjustment.

Practical Aquaponics.

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24 thoughts on “Mineral and Nutrient Supplements in Aquaponics Systems.

  1. I would like to know what type and were should I get the following items from this page.
    Cheated iron

    • Hi Jimmy,
      Chelated iron is available from most garden shops. It is most often in powder form.
      Potassium is most easily found in the form potassium bicarbonate. This can be purchased most easily from “brew” shops. It can also be obtained in some garden shops and is sold as an organic foliar spray to assist in the control of mildew on plants.
      Calcium is obtainable at builders hardware stores as “Builders Lime” or “Hydrated Lime” This is used to adjust pH when necessary and happily adds calcium to the system in the process.

  2. Thanks Murray

    I appreciate your time. I feel like my system may need something because although my plants are growing they don’t look as vibrant as yours do. One thing you mentioned in that page was that the plants could all of a sudden the could stop getting nutrients from the fish. I feel that has happened to me a few weeks back. When it did the amonia spiked and I was out of town and all my fish died. So I cleaned up the mess and started over. I want to try and prevent that this time. I’m hoping to maybe meet you in Orlando at the 4day school one year but not this one. Anyhow Thanks

  3. what about ATAMI Alga-C ?
    Is it a seaweed like your Seasol ?
    Hope it is not harmful for fish.

  4. Hello, we have a floating raft system over a 300 gal. tank with talapia fish. Our strawberry plants are showing what I think is calcium deficiency , browning around the edges of old and new growth. Our pH is running a little high 7.2-7.5. Any info would be greatly appreciated. Thank you, Gena

    • Hi Gena,
      Calcium is easily added by using hydrated lime, this will however push your pH up. pH can be lowered by using hydrochloric acid. It is cheap to buy, use sparingly, wear gloves and eye protection. Us a cap full, wait a couple of hours, re test the pH and see how it went. Repaat as necessary.

    • Could be a potassium deficiency, especially if your strawberries are trying to fruit. It’s good to test calcium before adding calcium…too much calcium can interfere with potassium absorption.

  5. My plant steams are turning purple. I believe magnesium deficiency. Will garden lime cure or what is a good cure for aquaponics system that wont hurt the fish

    • Hi Steve,
      Most of those micro nutrient problems can be fixed by the application of seaweed extract. Choose a good brand such as Seasol in Australia and Maxicrop in the USA.

  6. Hello Sir Murry,
    I received your direction on the iron, however not on potassium, and the magnesium, is there a guide line on those?
    My sincere thanks, michael.c <

    • Potassium is usually added as part of pH adjustment. Us Potassium bicarbonate. It can also be used as a leaf spray to help control mildew problems while adding potassium to the plant

  7. Murray

    Is that the same as potassium hydroxide. and also is it Calcium “hydroixde” that I should be adding also.

    • Hi Jimmy,
      Potassium Hydroxide is OK but is very strong. Better to use Potassium Bicarbonate. Calcium Hydroxide is OK and so is Calcium Carbonate.

  8. Murray
    Thanks for your response. I do always appreciate your time and answers. I was not questioning you but I was told by James rakosy to use the Hydroxide make up to both of those supplements.

  9. Potassium Hydroxide is OK. We use it around here but I always caution folk as it is very strong and it is easy to overdo its use.

  10. Hello Murry,

    I am teaching a group in China about Aquaponics. Something I didn’t foresee, but should have, was sourcing these supplements. Would you know a good global source that won’t kill me on shipping for chelated iron, potassium, calcium, and the test kits for pH and minerals?

    I can get seaweed extract here. It comes with recipes to make lotions and face masks… Same stuff? Is there something specific I should be looking for on the label? The name brands we are used to just don’t exist here.

    Thanks for your time,

    • Hi Sully,
      WE supplement with a good quality seaweed extract. That does most things. Make sure it is just seaweed extract and does not have a lot of addatives. Occasionally you will need to add potassium, calcium and iron.

      Contact me further if I can be of assistance

  11. I have a 70 gallon PVC aquaponics system. I need magnesium, potassium , calcium and iron.. I want to get the fish/kelp concentrate, also. Where can I buy these and where can I buy test strips. I live in EcuAdor and these things are not available here. I have someone who will ship this to me but I need to find these things. PLEASE HELP!!

  12. dear Murray, I’m having some sort of deficiency in my system and am low on funds I opted to try a small amount of eggshells, wood ash and a rusty piece of metal, do you think this help or harm my system?

    • Hi Travis,
      It is unlikely to make much difference either way unless you are very intentional. The egg shells should be nuked in the microwave before adding to the system. Put them in an old stocking or similar and bury that bundle in a grow bed. Same with the wood ash. Become a master composter and add compost tea to your system. Worm tea and worm castings are also a good natural way to add the trace elements to a system.

      • just like PH goes up w Calcium additive… whats the result of adding potassium additive?!?!?! any cautions in comparison of PH going up w calcium adding? or does it not have any down side affect or negative affect?

        • Hi Andrew,
          Potassium sulphate will tend to push the pH down. Potassium hydroxide, potassium bicarbonate will push the pH upward. Potassium in general is good for the plants and is non-harmful to the fish when applied in quantities that suit the plants. Potassium should not be added at the same tome as the calcium supplement.