Hello, After keeping several fish and inverts in a few very small tanks I am preparing to get my first larger tank started. It will be a 55gal tank that is 48" long. I plan on using small/medium gravel as the substrate. I could use some help ensuring that all the fish will work together as well as need some info on filtration and such. First, here are the water parameters of my pure tap water: Nitrate, nitrite, Chlorine, ammonia = all 0 Hardness = 300 Alkaline/kH = 300 pH = 8.4 Now for the fish that I am considering: 15-20 Cardinal tetra 5 Rasbora 2 Bolivian Ram a few Cories, maybe a couple of banjo catfish I am also interested in adding a couple of rainbowfish, not sure which type yet. But I have been told by someone that rainbowfish need to be in groups of at least 6? Anyway, can anyone verify this setup or let me know if the rainbowfish would work in a group of 2-3? Any other fish suggestions to add to this group? Also I do not know anything about filters for tanks this size, can anyone direct me to some filter options? Thanks!