I don't have a picture but I have a 33 gallon clear sterilite plastic tub buttressed between the windowsill and a piece of furniture to wedge in the sides, and I used dried dirt (a lot) mixed with a lot of dried grass clippings, and massive amounts of leaves on top. The water is good enough to drink but requires some plants to get the dirt moist enough, but I use rainwater, as tapwater becomes foul (have a bubbler running, and wavemaker occasionally). But I don't have any sand or gravel on top, but the dried grass mixed in, and the leaves on top keep the dirt good. It also helps that I put the container outside in direct sunlight for two straight weeks until it started to smell like farm manure, as that helps add some foam to the water.
I think it would be good to have a composter outdoors, and you could put some small amounts under the leaves for foam. I think you could also have a small composter indoors with a heating element because its the contained volume with sunlight that heats it up like a greenhouse, but if you want foam (and not algae like mine leaving it outdoors, had to bring it in), a composter filled with dried grass clippings and unsalted things could be added and would add foam and probably counteract algae growth from a planted tank, due to the foam like at the base of a dam (it would be foam that's not from sunlight in the composter). I would think a heating element could keep a composter initially above 100 degrees for rapid composting. But as it stands now, with the large amount of dirt and natural algae I wouldn't put fish in it, but adding compost foam may kill off the algae.
Possibly could use an aquarium heater in a small contained composter, and search for reactor on this board, the gases produced from the composting (as long as what's in it is reasonable) may be better than just CO2 there would be more gases. But the reason why I have dirt is that the normal aquairum bubbler (I don't have a reactor or composter) mineralises rainwater, so it's not harsh to drink, so you wouldn't add the harsh composting elements but the gases produced being released slowly into the aquarium. A light bulb in a closed container with things like dried grass clippings and some water might be enough to compost it.
Last edited by ntdsc; 08-22-2019 at 09:02 PM.