Plant nutrients

[anniefish]

Hi all,
Just a question about trace elements and minerals. Does any one know if plants grown in aquaponics receive all nutrients even in trace amounts? Do we need to add anything?
Cheers Ann

[Hamish]

Hi Ann

I think most (if not all) of what they need comes from the fish waste. The minerals etc come in the form of fish food.

Chelated Iron is sometimes recomended if your plants are looking a little yellow. But aparently only very small amounts are needed to reverse the yellowing - so a packet should last ages.

I am trying to feed as much self grown food to the fish as possible - duck weed and black soldier fly larvae - so it will be interesting to see how the plants go on the nutrient front.

[gavinl]

Hi Annie

I suppose that the only nutrients that plants can receive come from what the fish are feed - plus any suppliments. It would be very interesting to obtain a fish poo analysis to determine if all dietary requirements are being met - especially, if only using fish pellets. I guess that if soldier fly larvae are fed a wide variety of waste, then it would be possible to cover the trace elements needed for plants.

gav

[Jonty]

Hi all,

Most of us use Seasol on our plants occasionally. It is made from seaweed extract and fish. It contains trace elements. Usually the only problem that occurs is the uptake of iron, especially if pH is too high. Use chelated iron as Hamish stated.

You can check out whats in Seasol here.
http://www.seasol.com.au/images/asse...l_1_7_2007.pdf
Regards
Jonty

[Outbackozzie]

A lot of AP systems are deficient in Potassium as well, seasol contains all the stuff that fishfood doesnt.

1 Cup of concentrate (250ml), twice a month per 10,000 liters of tank water works well.

[Jonathan Dyer]

If you are using tap water or better yet underground/dam water for you fish tank there are trace elements in there as well. Sometimes not much at all but depending on the water there may be quite a bit.

[Cockatoo]

Hi Ann

I am trying to feed as much self grown food to the fish as possible - duck weed and black soldier fly larvae - so it will be interesting to see how the plants go on the nutrient front.

I'm still researching aquaponics before building a system and am really interested in just how much fish food can be generated within the aquaponics system. If real sustainability is the goal then I'd like to know how little one can get by without buying fish pellets etc. Im very impressed with BSF larvae and have been feeding my chooks for months and will be keen to grow duck weed this winter (in the tropics) but if aquaponics is thought to be a possible large scale sustainable people feeder then it boils down to how well a system (with its only extenal imputs being water and sunlight) might be able to feed itself and us. If we have to rely on fish food that may include another species of fish caught elsewhere and possibly unsustainably then maybe we haven't moved as far as we would hope.

Cheers, George "Cockatoo"

[Murray]

The feed for our fish is one area that needs some energy input.

To produce BSF is not all that hard really and depending on the fish species (Jade Perch) waste /left over salad greens and the like can be used to good effect.
The trouble is that most folk are not willing to put the time into BSF or a worm farm or the like. A lot of modern folk are totally disconnected with their food source and have no idea that it takes labour and planning to produce food.

Commercial fish pellets are the easy way out...very convenient.
Generally thought not to be sustainable. But having said that, someone needs to make those pests, the carp, into fish pellets. That would be a good use for the carp and help reduce the infestation in our rivers. Most commercially available fish pellets have soy included in the mix. Some folk are very much against the use of soy.

There are many ways to solve the problem. As aquaponics becomes more accepted then we will find that inventive people will come up with good food solutions.
The important thing is to get started down the road toward self sustainability.
Every step toward that goal is very worthwhile.

[aussieap]

Lotta work being done atm by the big fish pellet producers on reducing the fishmeal input into their food. It won't be long b4 they have a pellet with zero or minimal fishmeal input.
BSF are a terrific supplement. We need to be a bit careful tho. Their exoskeleton has a high chitin content and this has low digestibility. They are also high in fat which for fish like a jade, prone to laying down fat, could be an issue. As an integrated part of the total fish food picture tho, they are an excellent supplement.

[Dufflight]

The chitin will also help by flocking. Making the water clearer. If you vacuum the tanks this will then remove the chitin.