the fact that he has to "top off" the water level in the tank is like doing mini water changes. i'm guessing that the water evaporates (where else would it go in a tank that doesn't leak?) fish can survive neglect way better than "over caring". it seems like the more i used to think about my fish tank and try to make it better, the more fish died. then, i stopped caring about the tank, stopped doing water changes, fed them when i remembered, let the algae grow so much that you couldn't see the fish....and they grew and survived. i'm better now about feeding them twice a day and i got an algae eater, but i only do a water change if the fish are acting weird, like not eating or not swimming a lot...and then i only take out 2.5 gallons out of the 20 gallon tank.