So with my biocube I guess I was lucky. I had no idea how big a deal evaporation was. Now that the 40 is starting to cycle I'm noticing the water level in the sump dropping daily and salinity going up and up. I do have an ro/di system to replenish the water but what I really want/need is an A.T.O. system. Can anyone recommend and decent cheapish ato? Anyone have one for sale they want to get rid of?