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The good old questions: what fish and how much of it?
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Author:  AndreiB. [ Sep 24th, '20, 21:18 ]
Post subject:  The good old questions: what fish and how much of it?
Location: the Netherlands/Europe

Water temperature conditions: no heating or cooling devices. The temperature can vary and it is subject to the T outside. 5-31 C or 41-87 F throughout the year. Basic water heaters can be added.

A. TOTAL HYDROPONIC GROWTH AREA

Tubs + Dutch Buckets + NFT + DWC = 11.4 m2

B. FEED REQUIRED PER SQUARE METER PER DAY (according to the FAO aquaponics book)

The aim is to grow leafy greens and herbs

11.4 m2 * 60g/square m (for leafy greens and herbs) = 684g/day



What am I looking for?

Fish that can withstand these temperatures and are edible (preferably)

Possibilities that I looked into:

- Monoculture of Pike Perch (although very sensitive to water quality and overall stress)
- Polyculture of Koi and Goldfish (although requires a lot of space)
- Polyculture (in different tanks) of African CatFish during summer (in one tank), and Koi/Goldfish throughout the entire year (in another tank) - (although, when harvesting the catfish, the system may endure a shock; attention must be paid to the number of plants as well during that time. Concerns about the transmittable disease)
- Polyculture (in different tanks) of African Catfish and European Catfish (same concerns as above)

What are my questions?

1. What type and how much fish to sustain the mentioned plant growth area? example : fish stocking/ cubic m
2. How much water volume is required to grow the selected fish?
Author:  danny [ Sep 25th, '20, 22:45 ]
Post subject:  Re: The good old questions: what fish and how much of it?
Pike perch, aka zander, are very light sensitive and prone to stress unless kept dark.

European perch are good eating and will withstand those temperatures well.

Having a large volume of water and good insulation helps reduce temperature fluctuation. Having the tank sunk into the ground is ideal.

heating is pretty expensive, and in the winter when there's hardly any light it might not be worth ait as plants will hardly grow anyway unless you add lighting!

In the spring when there's more light but its still cold you can pump the water through a lot of black tubing in the sun to get temps back up a bit quicker. quite a few people on this forum do that.

Stocking trout fingerlings when temperatures drop sufficiently at the end of summer and harvesting them the following spring would be another option, with some perch to keep thins goin.

The most important determining factor when decidong how much fish is the amount of surface area provided by the biofilter. Most people go with a rule of thumb which is

"(.5 kg) of fish for every 1 sq ft (.1 sq m) of grow bed surface area, assuming the beds are at least 12″ (30 cm) deep."

so 1 cubic foot of wet media per .5kg of fish.

for trout the typcal average feed rate goes from around 2% when small (4 iches) to 1% when large (12+inches). So if you want to feed 684g per day to sustain you growing area you're talking 27g trout of 250g, eating 2.5g each per day... 275x2.5 = 687.

they would require around 140 cubic ft of media. or roughly 4 cubic metres.

perch have a slower metabolism so you can have a few more on the same amount of feed and biofiltr media.
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