Keeping them in exact conditions breeds weaker shrimp, I will cop a bashing for that one but its true. All water has a cool season and a warm season even the tropics, so for health let the cool a bit, Make the comparison to us, if we live in a constant warm temp and get exposed to cold we get sick, if we are exposed to cold temps some times we are more resistant, I fit into the first one hate the cold. In the wild the Temp swings lots, BUT it swing slowly and can be as much as 10 deg or more once again slowly. I let mine swing and I lost some of the originals but what is there now is tough. I was going to jump on the soap box, but no, selective genetics mainly for colour weakens any thing as we can not test for physical resistance and strength, just a thought no finger pointed at all Bob PS bash now