Do you still have the stock pump in it? Mine ran way too warm wit that (plus it was noisy). I changed it for a minijet and I fixed the noise and temp at the same time.
I have a 05 24G nano and for summer I actually changed the light cycle to come on at 4pm so its off during the day and on at night..I dont have a issue with heat anymore.
I also have a new pump but never saw it change my temp any.
You may need to vent the canopy a bit, by leaving the access panel open or using something small to wedge the top up 1/2" to allow heat to exit more freely.