Backyard Aquaponics
A place to discuss aquaponics

the ratio is *wet media* to fish - because that affects nitrification.
Surface area is afactor *but* if you have a shallow grow bed then you cannot grow many plants anyway.
The 25L is optimal for 300mm (12").

with deeper beds you have more wet media because the top 5cm or so doesnt count (it is 'dry').
the sort of tubs you are using are fine.
you just need a few of them to get the volume up (in a larger setup).

At 100L you are able to support 4 fish.
(but keep in mind that the fish also need enough room to swim around and live a stress free life).


I think Greg underestimated the size.

another thing you can do is ditch the siphons and run CF until you get a better fish tank.
Those 100-150Litres tubs IMO are only good for a couple of yabbies.
Get your IBC and use that tub as another grow bed.

** if having trouble with a full size IBC try cutting it back to 500-600Litres.
That will make it easier to transport and move into a confined area.

once dismantled and cut down they are easier to handle.
You can always ditch the metal pallet and just keep the cage.

Total wet media volume, it's all about the surface area for the bacteria to colonised to convert the ammonia to nitrites then into nitrates for the plants which in turn filter the water for the fish. Circle of life sort of thing.
So 90 litres total of media at 250mm deep with water height at 50mm below the surface and s only around 75 litres wet media and 1 fish per 20 litres (rule of thumb) is only 3-4 fish. Comfortably.
This is a basic calculation not taking into account things like feed input, fish size, flow rate, water volume and so many other variables.
It's always easier to add fish than remove dead fish...
Getting a system started regardless of size gives good education and a jump forward when expanding, perhaps even some vegetables too.

Ah! That makes sense. I was thinking of the plants in the media and ignoring the bacteria in the media.