You can fill small soda bottles with water and chill or even freeze them and add them to your res, although in a very small res this may not work.

No matter what, you should try adding MORE oxygenation. If you have one airstone, add 2 more! The zyme products are fantastic but really need a good, well-aerated environment to work... as a matter of fact, so do the roots themselves!
stinkyattic Reviewed by stinkyattic on . Plagued By Root Rot Indoor Grow Method: Hydroponics Medium: Hydroton System: 2 DWC buckets Water Source: Tap Water pH: 5.5 (constant read, calibrated 3 days ago) Tap Water PPM: ~300 Plant Age: 5 week old clone, Day 4 of flower Nutrients: Pure Blend Pro Bloom and Grow (50/50 mix) and Hygrozyme Current PPM: Was 1,000, 750-800 since root rot Rating: 5