Try cean up the area with a bit of sandcloth/dry it up/make sure pump to sump is off/try silicone the affected area...leave pump to sump off for at least an hour...nothing is guaranteed but it worked for a friend of mine
And if that still does not stop it clean it up re silicone the area and than rap teflon tape around the wet silicone, that worked for me once
__________________
its time to get up, dust myself off, and begin the process of rebuilding my tank!