How hot is too hot

[Delphinus]

You can lower the tank temperature to lower than that of the ambient through evaporation, which is pretty keen. So you can always add a fan blowing onto the water's surface if things really get out of control. So I would try this before I invested megabucks into a chiller. The only downside to this low-tech solution is increased evaporation means increased humidity.

I don't really know what I think of the higher temperatures. The one thought I have is that, if it hits 85-86 NOW, what's going to happen in July and August when it's actually above zero outside.

I think more important than a max temperature is the speed of temperature changes, and then after that, the difference between min and max. If it's a huge swing and it happens very quickly, I think that has to be worse than simply having a max temperature in the mid to high 80's. Some people don't have problems with swings but if temperature swings wildly from day to night, I have to think that this is harder on inhabitants than a mild swing or a temperature that doesn't really fluctuate too much. I think ultimately people will find their own comfort zone. I know some people (Brad? I think) get some pretty high max temps in the summer in their tanks and seem to do OK by it, but I have to admit if I see my tank hitting >85 I get nervous and start thinking about adding fans or in extreme cases, switching off halides. On those days those guys who have air conditioning, or chillers, have got it made. It's just that, in Calgary, it's probably, what, 2 or 3 weeks out of the year where this tends to be a real problem.