Heater dilemma

[asbury030]

Well I have a 20 gallon reef I got going with a 10 gallon sump/refuge my question is I plan on putting the heater in my sump. Since there is really only about 10 gallons or less running through the sump at a time could I use a smaller heater or do I need one rated for around 30gals? I just am limited on space so smaller would be better. 

 

[geridoc]

Your system has a little less than 30 gallons in it. I would put 2 heaters, each suitable for 20 gallons, in the sump. That way, if one fails in the on position (they always do), it won't be able to cook your tank.