Compensation... I can't remember for what... Oh must be a small bladder.

I figured the sump would be a good idea for auto top off and the heater not really much for increasing water volume...

LOL! Yeah, small bladder, that's gotta be it ;-)

I top up by lifting the lid of the AC Mini and pour the top up water into the filter chamber. I guess my need for compensation is pretty miniscule, and cheaper too :-)

I like to buy toys... the pet store loves me, I like to buy toys... the pet store loves me... yadda yadda yadda... lol