I try and keep my 100 gallon reef around 80-81 degrees...I normally keep 2 heaters in my sump which both are 300 watts....I put one on about 78 and the other around 80. Noticed the other day that the tank was getting warmer and warmer. Had the highest one on 80 and the tank was 84....took the one out and now Im having issues keeping the temp stable. Also I have a 40 gallon sump too....I think one is a Visitherm and not sure on the other....both are glass...
Does anyone else have temp fluctuations or issues? Anyone keep 2 heaters in their sump? Also any recommendations on a good reliable heater? I set the one heater at 80 and the temp will only get to around 78...if I set it at 82, then it will only get to around 80...however if I set it at 84, it tends to go over 84...weird...both heaters are only about 6-12 months old.