I been having this problem, I have a Aquaforest oceanguard 605 running for about 2 yrs now. All of the sudden my display water and overflow water level raising making my ATO compensate for the low water level in my sump. I cleaned the return pump and adjusted the salinity for 1 week and today again the water level went up. Any suggestions of what can I do? I already played with the valve yo raise level in the sump. Thanks for any help