Yes fans are the best way to go especially if you can get it to blow across or just under the lights and leave the glass on to help cut down on evaperation. Ice is ok untill it melts so it is not a long term solution.
I decided am going to go with 3 fans. 2 on 1 fixture one on the other. I have a computer boneyard at my house so I am going to use old computer fans. I think I can build the cooling with just old 12V power supplies I have laying around along with the comp fans.
Have had this problem with commercial tank hood. 90g show tank doesn't have a lot of area in the hood for 4X48" fluorescents. Using 4 low-noise cooling fans from Allied electronics and drilled 1 3/4" cooling vents on the very top (used sexy plastic escutcheons to preserve esthetics!). I used more fans to get same airflow with lower noise figures.
I used an old power brick from an IBM laptop which was 15V and a couple of amps. A radioshack 3-terminal IC voltage regulator in a variable voltage configuration allows me to set the optimum airflow vs noise for the fans which is a must as the tank is right behind sofa in movie watching area.
Fans were about $10 or so, ea. Works really well. I was also getting in the 85F range during summer (which is back today again!). Tank will now stay down around 79F with ambient in the 76F range.
For $20 or so I bought the Radio Shack indoor/outdoor wired thermometer to monitor air temp in hood and w/fans it's about 90-ish and w/o fans it around 122F. Also use temp probe on that to set water temp when doing water changes...works great.
On the evap side...I have an in-ground pool and know by experience that 90%+ of heat loss in a pool is evaporation. If you don't mind maintenance of adding makeup water you might create vents in lid to allow fan air to circulate above water surface. This will enhance cooling effect significantly.
I'm planning to construct a homebrew Pelletier junction cooler(chiller?) from stuff in my junkbox. My tank is right on the edge when temps get towards 80F ambient, and my electric bill is already out the window (so I need to cool the tank and not the whole house!). I've found some info online for small ones that have been constructed but am looking at something that would make a real difference on 90g tank.
