I currently have a 30 gallon long (36x12x16) setup as a "south american" tank, with 8 bloodfin tetras, 7 mirror/blue tetras, 1 Oto, and 3 Julii Corys. Current pH is 6.7, temp 80, 0 ammonia, 0 nitrites, GH of 2.8 and KH of 3, and an O2 level of 8-9 mg/L. My nitrates never rise more than 15 ppm...