I have a 5 gal tank, moderately planted, CO2 injected, 4 Amano shrimp, 4 cherry shrimp, 5 tetras, 2 nerite snails. Because of shrimp, I do 20% water changes every other day instead of 50% as recommended by EI method. Shrimp are thriving - molting and breeding. Under this arrangement do I need...