Setup a fan pointing across the tank as a form of evaporative cooling. I assume though that would cool the top layer of water more than the bottom and I wasn't sure if the differential in temperature may make things even worse?
A fan is a fantastic method for lowering a tank temperature efficiently; when researching methods to effectively cool a 60 gallon axolotl tank, I found several recommendations to use a fan. A small, two-head aquarium fan resting in the gap between the back of the hood and the back of the tank has been sufficient to reduce the temperature of that tank 10-15 degrees F or 6-8 degrees C. As the resident is an axolotl, a species capable of launching themselves out of their tanks, the openings in the hood are minimized and kept small enough to prevent her from fitting through them; even with this limitation, the tank stays consistently in the low 60s °F (16-20 °C), as measured from the bottom of the tank. As in other methods offered, convection carries the cold water from the surface down into the tank, allowing warmer water to rise back up to be cooled.
There are some caveats you'll want to consider with this process. You'll need to keep a thermometer in the tank (you should use one anyway). Because this method of cooling is much more effective than you may think, you'll want to keep an eye on it and make sure the tank isn't overly chilled, as well as be able to make adjustments to keep the temperature stable. Most aquarium fans have adjustable heads, which allows the direction of the fan to be modified; some may have separate controls for each head, or multiple speeds as well.
Secondly, because you're using evaporative cooling, your water level is going to drop much more quickly than it would without the fan. I do a weekly partial change and refill on my tank because of how far the water drops; if I let it go too much longer than that, the water level can fall below the upper inlet on the filter, causing the filter to stop drawing in water (and therefore stop working). Depending on your current tank maintenance schedule, you may need to perform it more frequently when using a fan for cooling.
If you need to manage cooling a tank for an extended period of time, a fan may be a more effective way of handling it than ice cubes, requiring less frequent maintenance and producing a more stable temperature result. Aquarium fans are generally rather inexpensive and can be easily acquired online. That said, if the period of cooling is only a day or two at a time, ice is effectively "free" compared to the fan and the time spent managing the tank temperature may be balanced by the reduced time doing overall tank maintenance and refilling it. For my own purposes, requiring the tank always sit below 65 °F / 18 °C (with ambient room temperatures around 70-75 °F / 21-24 °C), a fan is a much better option for me than using more temporary measures; if your tank is generally at the right temperature with only occasional spikes, then you may find less benefit from constant cooling.