If the PC's are causing the rise as they do in my tanks, here is my "poor man's" chiller unit.
Go buy bottled water in plastic bottles. Pick a size that will fit in your filter or that can be floated in the tank.
then freeze the bottles and float them in the tank or place in filter. In the summer a few per day worked well and kept temp under 80 degrees even though we have 100+ days here.
The water stays in the bottle and does not alter the salinity. Works great!
![Stick Out Tongue :p :p](data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7)