Hi all. I'm about 5 months in now and am pleased to report a healthy tank and inhabitants. But, and it is an annoyance, my gravel is always filthy. Is it better to use sand? Or, is there a better way to keep on top of the cleanliness of the dreaded bottom of the tank? I have cut feeding down - beginner's error - and the tank is cycling fine. I change water and use a gravel cleaner weekly; literally makes the water filthy for a few hours and, although I get a lot of filth out, it is a never ending vicious circle as the filth that comes up from the bottom will just resettle again - the only fix would be to replace the entire contents of the tank, obviously I wouldn't do that! TIA.