Water Temperature Question.
 

Hi,

I got a problem with my very small tank. I have a 2gal planted tank with a
28W light. Since the bulb is very close to the surface of the tank, it kinda
heats up the tank. The problem arises when I switch off the light. The
temperatures dips quite a bit. With this constant fluctuation, my fishes
fell very sick (white spots) and some died.

My question is, besides adding a heater which i can maintain at 30 degrees
celsius, so as the difference will not be too large, is there any other way
I can cool the water even though my light is on?

cheerios
Vincent