The problem is I dont have room for a HOB filter because in the back of the tank I have a fan to cool the water down
Sides? Your going to change water like crazy anyway so just get a sponge filter.
I wouldn't do a canister, but it's your tank. Hob, sponge, or plant would be the way I would go.
What are you keeping that needs the water to be chilled in a smaller tank like that?