Tidal pool critters are used to temp swings. At low tide the pools heat up and when the tide comes in they are hit with the cold right?
So why not use a feezer pack in your filter? Have 2 on hand, one in freezer and the other in the filter. It wouldn't drop the temp too much, but it would on a small level semi re create the natural temp swings of a tidal pool.
Might help until you get a chiller running. But then again, I could be way out to lunch here.
