About a month ago my 75 got brown algae (not a bad case) so i used tetra broad spectrum algae control and it worked well, soon after my algae eater croaked, and yes i fed him. After a week or 2 i decided to get a canister filter to replace my old emperor 400 that was starting to have issues, so i got the XP3 and ran it with my emperor for over a week to work the bacteria into the new filter, bought a cat and another algae eater and both died in days so i tested the water and everything was fine but the nitrates were like 160, no nitrite, did like 40% water change, also bought the bacteria starter and just got the nitra-zorb in my canister about 2 days ago and it's still 160. the emperor is off and the only other thing i have is a bubble wand under the gravel for extra oxygen. my tank is mainly cichlids. All bottom feeders and algae eaters dont survive also have 3 fry cichlids and they seem so be fine, i've never had a water issue before, thx.