I’ve never used the computer fans myself, so I’m not sure regarding all the details of how to wire them for cooling the aquarium. As I understand it, you’ll also need to obtain an AC adapter for each computer fan; the computer fan is wired to the AC adapter which is then plugged into an electrical outlet.
I prefer to use chillers or the clip on fans that are equipped with a cord and already to go right off the shelf when I need to cool down one of my tanks, as Leslie Leddo described below:
Fans work great for decreasing tank temps. Small 6 to 8 inch plastic electric clip on fans are available at most home improvement centers and places like Longs or Rite Aide. They can be clipped on to the tank rim and adjusted so that the air from the fan blows across the surface of the water rippling it a bit. This works very well. I would suggest 2, one on either side of the tank.
It does increase evaporation quite a bit so you will need to top off more frequently.
It is also a good idea to use a heater set at the the low end of the goal range. If your tank is 78 without a heater start by setting it to 76 with the fans running and decrease it by 2 degrees every day until you figure out just how much the fans will bring that temp down. I am guessing with 2 fans you should be able to keep the temp about 75, which should be just perfect.
I should also caution you to observe all the usual precautions to prevent shocks and electrical accident when you are using an electric fan or any other electrical equipment on your aquarium, Sandy.
One such precaution is to install an inexpensive titanium grounding probe in your aquariums. That will protect your seahorses and other wet pets from stray voltage and should also safeguard them electrocution in the event of a catastrophic heater failure or similar accident..
But the best way to protect you and your loved ones from electrical accidents around the fish room is to make sure all the outlets are equipped with Ground Fault Circuit Interrupters. And it’s a good idea to make sure all your electrical equipment is plugged into a surge protector as well to further protect your expensive pumps, filters, heaters, etc. from damage. Some good surge protectors, such as the Shock Busters, come with a GFCI built right into them so you can kill two birds with one stone. So when you set up your cooling fan(s) on the aquarium, be sure they’re plugged into a grounded outlet with a GFCI or a surge protector with GFCI protection.
Best of luck with your pipefish and seahorses, Sandy! Good luck beating the heat and cooling down your tanks.