[Sebae again]

The pull down is how many deg. you can lower the temp. If your tank is at 78 f now at 68 f room temp ,at say 90 f in the summer if you don't have airconditioning then your going to burn up 22 deg of your chillers capacity to maintain the tank at 78 deg. Dont forget that the pump you use for your chiller is going to add some heat as well so the chiller has to work harder to overcome that. For my 90 gal ,I was recomended a 1/6 hp chiller.I said no and went with a 1/4 hp and I'm glad I did because my chiller runs a lot and a 1/6 would have never kept up.