When directing the fans, make the most use out of blowing the water across the longest surface axis (left to right) with not only to help with evaporative cooling, but pushing out the heat. Though your current design may be unobtrusive, it may not be as effective as a cross cooled design.
Think of it like a power head, if you hit the wall, some velocity is lost.....you want to not only be using evaporative cooling, but pulling in cool air while pushing out the hot. If you can get rid of the heat before it sinks into the low energy resevior (water), then your job is half done.
If you have a sump, double up there with the fans.....remember the water is what is hot and that is throughout the entire system, lowering it in another, possibly more efficent area of the tank, is just as effective if not greater.
Try running your lights during the day when the house is the coolest and shortening the time your lights are on if that is possible, this way you have more of a low temp resevior that can absorb the heat from the lights. (run them in the morning or late at night, avoiding the mid day when it is warmest or in the early evening while cooking)
If you can, increase the surface area of the water exposed to the air, but that would take a sump redesign and isn't the easiest.
If you are using your chiller, make sure the flow is matched for the system.....Even though my chiller is rated for my tank, I try not to forget cleaning the pump to ensure the proper flow.
If you can, raise your canopy an inch or so when you aren't trying to show it off and make the tank look presentable.....sometimes function wins out over form......
Use frozen bottles of ice to pull out the energy of the water.
How many pumps are you running? Are they all needed, can you set your controller if you have one to shut down a few pumps at a certain temp? I just bought a Vortech and by removing 2 Seios lowered my temp by 1 degree F, but $400 buys a lot of chiller run time.
Are you trying to keep it too cool in the first place? It has been shown that the reefs in the summertime, when the corals grow the fastest the temperature can be upwards of 81. Personally, I don't like to push that due to the accuracy of hardware and not giving one some "buffer" for clamity, but if you are confident of your temp readings, there should be no reason not to approach that number.
If your dead set against buying or using a chiller, I suppose one could load an icechest (large one) full of ice and run a lot of vinyl hose coiled through it. This trick is used in drag racing as a "cool can" to chill the fuel entering the carburator to make the charge denser and avoid vapor locking. The increased volume in addition to the ice chest full of ice could be quite effective and last a decient amount of time.
