For me, it’s barely enough to just open the cover. On another aquarium, I’ve had to put a fan on it. This 25l aquarium went from 27°C down to 25 with the fan.
I have 240l with Axolotls and set of fans was doing barely anything. I got a special water cooler that stands between filter and the tank. Loud as hell so not an option for a bedroom, 400 EUR, but keeps the little rascals below 19 degrees C even in the top of summer heats.
There are various sizes available, so for smaller tanks some cheaper option would be available
I think that I’d go the diy route: Computer water cooler loop cooling the aquarium water: Either with these peltier cooling things. That’s just an idea, it’s not tested. Maybe sb else has done that somewhere.
Good luck and do share your solution once you have it :)
That’s just a heat exchanger with the surrounding air.
- If you need to go under air temp, anything else than a cooling system (think fridge) won’t be enough.
- if you need to drop close to air temp, afaik the best cooler for a water tank is surface evaporation. There might be a diy way trying to increase evaporation (water circulation on a ramp with fans blowing on it or such).