Hi my daughter was maintaining our tank while we had to go out of town the nitrites are still high their is actually more like 30 lbs of live rock the tang looks great and the eel is eating and looks good I was also scared of the waste from the eel but was recomended by fish store I think maybe we should do another water change or get new carbon or both ???????? I have another bio 400 filter should i hook it up allready have 2 of them running now