okay guys, just did a 50% water change with ro/di water that i filter myself with the kent brand ro/di filter. i tested the fresh salt mix and the nitrates are 0. all day yesterday i used a powerhead with a hose attached to it to blow off the liverock, to get all the deitrus off of them and into my sump. during the water change, i cleaned out the sump, foam pads and everything that could hold deitrus. i did not vaccum the sand, because when cleaning the liverock all of the surface was cleaned too. so i replaced the saltwater with the fresh mix and tested again. the nitrates are still off the charts. the only thing i can think of, is it's got to be my sand. i guess with my velvet damsil blowing the sand around to make a cave like home behind the rocks, the sand isn't deep enough to be anaerobic for the bacteria to live. i'm thinking about vacumming the sand, afterall it would be no different than having a bb tank. right? if the liverock houses the nitrifying bacteria, vacumming the sand shouldn't cause a crash---i hope!! unless the bacteria moves to sand and every water change would reduce their numbers over time. my sand could be too deep for shallow sb and not deep enough for a deep sb. i am soooooo confused!! damsil (1.5 years old)and green brittle star(2 years old) small group of button polyps which is barely hanging on, good color(brown with neon green centers) but not expanding tentacles. thats all i have left after a mass kill about a year ago. back then i had no sump, skilter 400, fluval 307. one day i turned the skilter off because it would always clog up and run over the top of filter pads and fill tank with micro bubbles. knowing the fluval 307 is rated to run tanks up to 75 gallons and mine was only 29, i just left the fluval running. not thinking, the tank didn't get any oxygen because the return line is under the water level. i have to say the velvet damsil is one tough fish, lost it's color, but the only fish to survive.the fish and starfish are doing great now, but i do have a reeftank and want to grow corals. just trying to figure out what to do. any help would be appreciated.