Fighting a losing battle...
Adam Stone said:
wouldnt adding fans to the lights help alot?
Well, yes and no
...
Assume your tank is sitting in your room with no equipment running, no lights or heaters on, and no evaporation taking place. In this scenario, your tank really can't be any colder than the room.
Now I don't know how warm that room gets, but if your tank has already hit 89F, and with the hottest days of summer to come, I would imagine that you are going to push (and ultimately exceed during a heat wave) the limit of what the tank inhabitants can survive.
Most corals cannot tolerate temperatures above 85F, and the warmer the temperature in the tank, the more likely it is that fish will start to undergo stress and ultimately perish; the warmer the water, the less DO it can hold. In ither words, the fish start to suffocate
. If I were you, I would desperately not want to have a repeat of 89F
, let alone anything above 84F.
Now back to the tank sitting in the room with no equipment or lights running. If your room reaches 89F during the day, eventually, the tank will reach 89F. If you turn on the lights, pumps, and powerheads, these are all additional sources of heat energy which will elevate the tank temperature above the room temperature. My tank runs consistently 5+ degrees warmer than the room even with a powerful fan and no canopy.
Fortunately, the process of water evaporating from your tank removes energy from the system, thereby lowering the temperature. Evaporational cooling is actually a very powerful source of cooling. It is why we sweat, and it is what causes us to be cold when wet, even on an otherwise warm day. So you are always going to have evaporation on your side (of course, that means more RO/DI water).
So yes, dissipating heat from the bulbs themselves with a fan helps, but the light transmitted by the bulbs will still warm the water as it is adsorbed by the tank and water, even if the bulbs were room temperature to the touch.
To enhance evaporational cooling which you get pretty much for free, I would suggest using one or two large box fans blowing air across the surface of the tank. I have a box fan on an x10 controller that turns on and blows across my Aquaspacelight when the MH lights turn on. It has done wonders. This might be hard to set up with a canopy, and if you are having heat problems, a canopy might not be the best way to go (or you may have to elevate it off the tank).
Now, will all this evaporation and heat dissipation from the bulbs be enough? I don't know, but probably not. You're best bet is to try and lower the temperature of the room with a window unit air conditioner unless you can place the chiller where the exhaust will be open to the outside.
I hope this helps,
Matt