i suggest keeping res temps around 66-68. any higher than 74-75 and youre going to have problems unless you are running a sterile res. a water chiller is ideal for keeping res temps in check, but they can be cost prohibitive. the frozen water bottle method can be effective, but it is not as accurate and can be tedious to maintain. you could also get a more powerful a/c. or you could discontinue any beneficial bacteria you may be using and start adding h2o2 to your res to make it a sterile environment. i dont know too much about the sterile res thing though, so i could be wrong on that one. do some research if youre interested in going that route. personally, i just got a beastly a/c unit and that takes care of the res temp issue for me.
