It is very difficult to chill an aquarium to a constant temperature without changing room temperature. The best way I think, the easiest way, which using an air-conditioner in the room: )

Frigid units

Teco TK500 (serves up to 500lt system) for 0,5 w / lt Heating load --> will not deliver 14 degrees in water if room temp is 25 degrees. Heating load (latent heat) produced by system equipment as well as thermal properties of surrounding space (room) will always influence the chilling capacity.

Teco TK1000 (serves up to 1000lt systems) for 0,3 w / lt Heating load --> more than enough

Dear Ms. Janja Ceh

It is possible to chill aquarium provided it is kept in constantly running air conditioned room or even using frugid units. So I agree to Baran and Susan.

Good Luck

In younger years, I kept North Sea fishes in an aquarium; these fishes preferred about the same temperature range of 14-20°C. As a cheap and simple way, the aquarium was cooled down using an old, used refrigerator. After drilling two holes into the side of the refrigerator, the aquarium and the filter tubes were isolated with styrofoam, then the water from the filter system was pumped through the ice compartment of the refrigerator, and back to the aquarium. This kept the aquarium at a temperature of 10°-12° below the room temperature; the temperature could be adjusted with the refrigerator. I used this cooling system successfully for several years.

Thanks to everybody for their answers. I'm particularly tempted to try the McGyver - like approach of Ronald Fricke :)! Again, many thanks to you all for your time.