Perhaps a mini tank of daphnia (water fleas) might help your system? Filtering with fish snack bonus!

[Brian White]

I don't do aquaponics but I do have a small fishpond with goldfish.  And up to this summer,  I could never see the darn things because the water was a perennial green color.   I put in a  top little tank (1/3 of a rain barrel) to airlift up  crap off the bottom of the fish pond and into it. It was pretty useless for that.  I added about a dozen daphnia (water fleas) into that little tank  and about 6 weeks later the water in the fishpond was clear.  Turns out the water fleas had bred and they eat the single celled green algae.  Interesting things for me is that cycling speed was not good,  AND I never saw a daphnia in the fish pond (presumably the fish ate them immediately they came in the overflow.  I think what happened is that the water flea babies (too tiny to see were eating the green algae in the fish pond and the adults tank  were acting as a nursery, sending a constant stream of babies into the fish pond. Hungry babies that ate the green algae in the fish pond!  Babies too tiny to eat until they molted a few times.  I think this may work on a bigger scale,  maybe even with the same small tank keeping a far bigger fishpond clear of green algae.  In my video, the air for airlift is about 4 liters per minute and another about 3 liters per minute was going to swirl the water in the fish pond. I used a 3/4 inch internal diameter pipe for the overflow but I should have used a larger diameter one.  Airlift up pipe was 3/8 inch internal irrigation tubing.