Petco just started there dollar per gallon sale so I figured now is the time to snag one for a DIY sump. I was thinking of getting a 20 gallon long tank as the sump. As of right now I want to put my skimmer and heater in the sump and have room for a refugium and also have some extra room for some other things I might add on down the road. Do you think a sump that size would be too small?