Hot tank!!!

I have a computer fan in my hood blowing on my Metal Halide and I have a clamp on fan blowing on my refugium. I lose about an 1" of water a day, but I stay around 79-80 degrees.

 

Here are the pics of my fans, and I have 2 250watt mh's over my 55 so your 150watt mh will be fine!
I also cut vents on each end of my hood and mounted the fans inside the vent on one side, so it is pulling outside air through the vent, blowing it the lenghth of the tank and exiting through the other vent. I keep my tank rock solid at 78, if the house gets up to 78-79 it might touch 80 for about a half hour during the heat of the day, thats it. But as mentioned before you will have to top off at least every other day. I still do it by hand with a 5 gallon pitcher, not as nice as an ATO but works nonetheless!
Also, as a backup I have frozen ziplock baggies of RO water in the deep freeze that I can toss in the tank in case of an emergency. I have tried them and it works like a charm, and is cheap insurance!

 

If you have the budget to get a chiller then they are a nice piece of insurance. It really depends on how much you have invested in your livestock. You also have to remember that if your AC quits in the house, how will you keep water temp???