SMiles

I'm looking for advice and opinion on what amount of water temperature rise is acceptable during an 8 hour metal halide lighting period. I have two, 250 watt mh installed in an enclosed canopy on my 70 gallon reef. I'm using two 4.5 inch fans for cooling which do a pretty good job, but I see steady water temperature increase of about 2/10ths of a degree per hour when the MH are lit. I have my temp controller set to maintain water (heater) temp between 77 and 78 degree f. The conroller is set to ...