between the lights and the fans my 8 cube evaps a lot of water. Are you checking the salinity with a refracting hydrometer, or just looking at the level of the water? Because the filtration area in the back holds a lot of water, and the level is always the same out front. there is a window on the side of the return pump side that shows the height fluctuation.
I might take out some SW
and add RODI
to get the salinity to 1.023ish and then let it evap away for the corals.
add an air pump to your five gallon bucket for the fish, and you will be OK. Watch the temps.