Backyard Aquaponics
A place to discuss aquaponics

but you will need to have gravel somewhere (or somethign for the bacteria to live in at least) in the system

Cheers

how about a large sealed bucket filled with gravel with say 8 6mmhomes drilled t=in the bottom circumference. it could sit in the fish tank, water in is from the return the flow pattern would be vertically down as the exit hoels are under water at the bottom of the bucket.

you could simply run an air powered old style filter... it would remove some of the solids as well as provide a place for bacteria to live ...
I hang strips of shadecloth in my student's wheeliebin to act as a surface for the bacteria to grow, and as a place for baby guppies to hide

Set up the wheelie bin with an undergravel filter like AA. The concept is good. The issue with root rot is if the water isn't moving and/or not oxygenated.
My thoughts (for what they're worth) is take the wheelie bin, put a false bottom in it, run a pipe under the false bottom (UG filter) pour gravel on top (not too fine or it will need to be cleaned and/or it will get gunky - 1cm size), then run your pipe up to the top pipe (as in the drawings). Let the drain be close to or in the bottom of the pipe. Use net pots with a little medium in it to keep the plants alive in case your pump cuts off (or a pipe comes undone), and run continuously.