Is Necessary To Agree Fertilizers For The Growth Of Plants In Aquaponics?

[jacobo]

Hi, I'm Diego from Colombia, and I am working in a aquapopnic system, I have goldfish and lettuce in it, but in the harvest, the lettuce was not good, they looks yellow,smalls... etc.

reading about the possible reasons, I found that the plants need some nutrients like quelates (for example of iron), and some hidroxides (for example KOH) for keep the pH neutral. and this substances are not in the fish food.

So What do you think about this?, is neccesary the use of this elements in aquaponics?

[GaryD]

Hi Diego,

Unless there are sufficient fish in the system to produce the nutrients needed by the plants, the plants will be deficient. Also, as you've stated, there are some elements which are not to be found in fish waste.

The addition of chelated iron will resolve the iron deficiency. In Australia, we use a product called Seasol to add some of the other elements which may be missing (or, if present, in insufficient quantities).

GaryD

[Murray]

Seasol is a sea weed extract based product.
You may be able to find a suitable sea weed based product in your area that will do the job of adding minerals to your aquaponics system.

[GaryD]

Diego,

The point that I may have failed to make clearly enough in my previous post was that, it your system is not producing sufficient nutrients for your plants, then it is OK to add them......so long as they are safe for your fish.

Gary

[Murray]

And further to what Gary has said, another factor is perhaps that your aquaponics system may be short on nutrients simply because you do not have enough fish. Aquaponics is about balancing the relationship between the needs of the fish and the needs of the plants.
Your system is out of balance.
The addition of nutrients in the form of seaweed extract or/and iron will help balance the needs of the plants, but you need to seek out the root cause of the shortfall in plant nutrient.
It may be that there are just not enough fish for the number of plants you are growing.

[jacobo]

Hi Gary and Murray, thanks for the answers, I think that the problem may be the population of goldfish. I'll introduce more goldfish in my system


By the way, I was talking with James Rakocy from the University of Virgen Island) and he said:

"The balance between fish and plants is determined by the feeding rate
ratio If you use raft culture the ratio should be 60-100 g of fish feed
per square meter of plant growing area per day. For example, if you
feed your fish 1 kg of fish feed a day, then your should have 10 to 16 m2
of plant growing area for lettuce".

So I think that is necessary to find the relation between food, plants and fishes...

[GaryD]

Hi Jacobo,

....the relation between food, plants and fishes...

The relationship between food, plants and fish is the very essence of small-scale aquaponics. The difficulty in balancing that equation on a large scale is why large-scale commercial aquaponics often disconnect the fish and plants from each other.

In effect, they use the water from the fish to irrigate their plants but they will often not return the water to the fish tank. Their operations are virtually a recirculating aquaculture system and conventional hydroponics alongside of each other. From a commercial perspective, there are a range of benefits in doing this.

The only linkage to aquaponics (as we usually understand it) is that the fish water gets used for the plants.....a noble enough outcome in itself.

Thanks for sharing the information from James Rakocy.......very interesting.

Gary