I think he meant inside evaporation, if i dont run my exhaust fan my basement gets humid in the summer from the 3 tanks lol. I have a 3x3 frag tank and i get a fair bit of evaporation, if you spend on 1 luxury item make it an ATO, it helps alot, otherwise in the summer you are probably filling a 1L jug every day to keep water levels up. Even worse in winter