[DeeKay's Fishies]

I've got a 30g tank set up w/ 2 dwarf gourami's, 1 angel, 1 pictus cat, and 1 small pleco. Ive been having problems keeping my nitrites and ammonia down to zero. The tank has been set up for some time now, but still wont even out. I put Cycle in for the bacteria and have done a few water changes, but still no luck. I saw this stuff at my LFS called NitraZorb. It's supposed to neutralize ammonia, nitrite, and nitrate and it's like a pouch thing you put in w/ the filter. I'm not sure what else I can do. I've already put in a million ammonia clear fizz tablets when the levels start to rise and its ok for a while, but tends to rise again. I dont feed them too much and change the filter. I don't know what I'm doing wrong, or if its just because it's a fairly new tank ecosystem. I just don't want all my fishies to croak. So any and all information/help is appreciated.