As someone who live in a tropical country, I'm worried about the heat. Right now seem to be no problem since it is rainy season and also I have air conditioner running when the outside temperature is high (air temperature can be as easily reach over 32 degrees Celcius or over 90 Fahrenheit).
Looking at the solution that I can buy, it is either cooling fans which are supposed to be able to lower water temperature by 2-4 degree or a chiller for aquarium which is too expensive and too much for my small 4.5 gallons tank.
Now my question is if cooling fans that blow across the surface of the water is enough, can I use air pump to blow air across the surface? Is that going to work if I only need to lower water temperature by 2-4 degrees? The reason I don't want to use fans is that I need to modify the lid to fit cooling fans and if I later change the fan or move to chiller solution, I need to get a new lid.
Another solution that require more work is probably a DIY chiller using peltier, heatsink and small fan that sit outside the tank and use water pump to circulate water through it to cool.