Sorry I'm so late to this , but fish farming is something I think I can help with
.
Out in New Bloomfield, MO, US I helped with a setup that is also a teaching place.
They use Tilapia as the fish since they are a good robust fish that lends itself to fish farming, even in old horse troughs
.
I've not yet read completely through the setup, but will very soon.
in the mean time can you give me a visual setup of what you have in mind?
the water is pumped much slower than your refresh rate. SO unless you plan on having an overly amount of fish in the unit, 50L/hour the keep the water aerated should me more than enough.
Out here/there the setup works like this: the outlet or the holding tank is setup at the bottom of the tank, so the effluence and water is caught and plumbed upwards with a "T" joint and short piece of PVC cut 1/3 top removed so the water slurry mix is allowed to trickle through the plant feeder bed made up of small gravel and sand.
You probably already know this as flood feeding, which cleans the water.
It works quite well, slow feeding allows the water to stay fairly clean , no algae growth and fish are grown the no more than 750g in weight.
Veggies grown successfully so far is Tomatoes now looking like small trees, green beans, ALL known leaf based herbs, Swiss chard (BUT can quickly get out of hand and grow too big to be tasty), and Peppers of various heat levels and colors, lettuce seems to thrive too well.
Kayle,eve grown directly from seed seems to be an attractant for aphids and we/they had to almost go with insecticides , but go everything under control with liberal amount of ladybugs, hand washing and getting the Kayle moved out of there to the outdoors where dish-soap and water could be used directly.
Light levels are keep directed towards plants using Aluminum foil, mirrors with light being kept as indirect for fish to lessen any possible algae growth.
Water is kept about 84F (29C).
It's been running more than 4 years this way with only items switched out was a non-contact pump motor instead of submersible ( I provided the submersible , since no one at that time thought about how they were going to pump the water
)
and fingerling catfish being added to see how well they would grow eating any possible algae and food missed by Tilapia.
Hope this helps
Bruce S