I've tried all sorts of things man, including setting up an radiator ciruclating my res water thru it and blowing air from the central A/C across it. Done the water bottles, done the fans, done the cooling of my air pump, and in all, I have spent more money trying to do it the cheap way...... Fittings, hoses, elecricity (for A/C or extra to freeze the bottles) just ends up costing more that just buying a chiller.... If your having temp problems, just save for a chiller. Oh, and INSULATE YOUR RESEVIOR's, or buy coolers (what I did).
ALSO: the best cure to cost ratio, is beneficial microbes. Since starting the tea my shits has been lookin awesome. You do not need much, 1-2 innoculations every 1-2 weeks is plenty. And it's amazing how well it works, you will notice results in your roots over night, if you dont have any bad bacterial colonizations to wipe out first....