I'd use something with a lot of biological filtration (like a mattenfilter) and use a gravel vac to really clean up the waste. If you have them eating high quality pellets and can keep some plants growing, they shouldn't produce that much waste. Once they hit a certain size, no filter is going to manage those turds.I've been looking at something like that for a shrimp tank, I didn't think it would work with such dirty fish. I'll look into it ty.
Well... Your lava rock will end up on top - it's lighter weight than most sand and sand will easily shift between the chunks of rock (even if it's pretty darn crushed). You're also working with fish who burrow and slide around on their bellies. Lava rock can be sharp (as can fluorite). If you're not too concerned about color, you could try a thin layer of pool filter sand mixed with a decorative type of sand or rounded gravel so you have a mixed grain size and accent it with big chunks of lava rock, maybe positioned around potted plants so the plants will stay in place.Lol, got ya, I have been going back and forth on sand, seachem fluorite and eco complete for this any recomendations on substrate,I had planed on basing the tank with crushed lava rock and laying my substrate on top