I'm currently planning out how I want to set up my 30 gal (36Lx12Wx16H) tank and really want to have a single-species schooling fish with several otos and snails as the cleanup crew. The problem I'm running into is that my water is quite hard (180ppm+) as it is from a limestone aquifer. This is quite troublesome as most of the great schoolers (rummies, cardinals, harlequins, espeis) are all soft-water fish. As of right now, I'm thinking about getting a school of Zebra Danios, but my question to you all is, "Are there smaller fish which school well and will tolerate/thrive in hard water?".