Yup there would be a fan blowing at the water surface as well.. as for the ballast, i'll just be leaving it as it is... see how things go, too lazy to drill another hole to cool the ballast (although I originally wanted to have it)
as for colour temp change due to the cooling effect, shrug, at most i turn off the fan... perhaps after I get my bulb I can run some simple checks on colour temp and temp with fan on and off... then can get some practical results..
Will keep you guys posted..