I stocked the gravel grow bed with red wiggler composting worms. I originally stocked it with one pound of worms; now they maintain a population that is probably over 100,000.

The composting worms survive underwater in this environment because the water is so well aerated that they can absorb adequate oxygen from the water right through their skin. They spend their days below the gravel feasting on fish poop, then come up at night and hang out on the surface.

Composting worms do several important things:

1) eat copious amounts of fish poop, thereby preventing clogs;

2) eat little pathways through the gravel, thereby constantly creating new little waterways through any area that does happen to get clogged;

3) after the worms get done digesting the fish poop, the nutrients are something like 6 times more readily absorbed by the plants (or so I've read);

4) they supply a food source for the adolescent fish that I keep in the side pool that I excavated out of the gravel. When a worm pokes his head into the fish area, the fish notice, and if they're hungry, the worm gets eaten. With so many worms in the gravel, there's a seemingly never-ending source of food for those fish. That also helps cut down on how much I have to feed the fish.