While those temps sound a little on the high side you may be ok. But as for cooling there are some options.
1) You can run the day/night cycle of the tank opposite that of the actual day/night cycle. This helps keep the tank cool in that the lights are off during the hottest part of the day.
2) You can isolate the lights from the tank with a sheet of glass and keep constant ventilation running across the lights. Which would limit their heating effect on the tank.
3) You could build a compact swamp cooler. This device forces in coming air across a network of plates that have water running over them. The result is the incoming air is cooled as its energy is used to evaporate the water running across the plates.
4) You could build a thermoelectric cooler based off of a few Peltier cells. Here are some instructions for the setup and curcitry: http://digilander.libero.it/westaustralia/terrarium/t-cooled.htm
I am working on a system that combines methods 3 and 4, to cool a 30 gallon Mantella aurantiaca tank. The pic below is it in the works. These are a high elevation species that will not take kindly to the heat of the summer where I am at. The advantage to this system will be in that it is based off a 12 volt supply, so I can have a battery backup incase of a power outage.
You may also want to consider, assuming you do decied to go with additional cooling, insulating the tank. This reduces viewing area, but can be done quite nicley (ie a foam background on 3 sides).
Just some thoughts,
Jay
