That's what nice about a remote res that recircs, you just put the ice in there and it never touches your roots.
The PC fans on the sides on the air pump really help to keep it cool, otherwise it gets quite hot while operating, which means it will pump hot air. If you can put your airpump outside your grow room, even better, the cooler the air you can draw with your air pump, the better. I also have a long length of 3/8" air hose coiled on the ground before it goes into the coolers, this is where it loses more heat created by the pumping action and comes back down to ambient. You can run your hand along the line and feel it getting cooler as it goes along.
Still though, if your ambient room temp is 80F, and you're pumping 70LPM pump in a 100L igloo, the water will pick up the air temp and heat up over time, coolers are supposed to be sealed, pumping a crapload of room temp air through them doesn't help them stay cool. Saving grace is most probably night-time temps when air is closer to where you want your water temp. Coolers do still help a lot though, with radiant heat and heat conduction.
One major reason I want to ditch the air pump next time and just go high flow water like Heath is so my coolers will be nearly sealed then, and much more easy to keep cool.
Watts is more applicable to talk about different pumps (water or air), as LPM or GPH is measured at a certain pressure, which for an air pump is based on how deep the water is that it's pumping into, and for a water pump, how high it must pump the water, AKA head pressure. Any manufacturer can tweak the stats to look better or worse, an eco 20 watt pump could list for 70LPM, while a high quality 60W pump might also be 70LPM but rated at a much higher pressure, which would mean more flow at lower pressures. Just for future reference, I notice everyone comparing pumps with each other's setups using GPH and LPH when we should be doing it in Watts, which is the actual power of the pump.
Another reason is because my 45W air pump is too powerful for my setup. When I had it running 3 6" stones in each 5 gal bucket I had a doughnut hole in each of my root balls from an overpowering torrent of bubbles, I can tell now from putting the air around the outside of the root zone that the roots are growing much better, and all the way to the bottom. If you wanna go the air route I'd really suggest going with high end ceramic air discs that really break it up into tiny bubbles. I think lots of people probably do more harm than good with too much air on their roots and don't even know it. If I were to run it again, I'd do it in my remote res, but I doubt I'll even do that. Maybe I'll take the fans off and use it as a water heater in the winter.