Factors to consider when choosing a chiller
When choosing a chiller, consider the size of your aquarium and sump, your aquarium setup, and additional equipment and the heat it generates. An estimate of the maximum temperature your setup may produce and the temperature requirements of your aquarium inhabitants are also very important considerations when choosing a chiller. In order to choose a chiller, you will need to calculate the amount of "pull-down" you will need. To do this, subtract the temperature at which you want your aquarium to be from the maximum temperature you think will be produced in the aquarium during the peak heat during the summer.
Choose a chiller that effectively cools your aquarium water in the space and setup you have allotted. If your cooling requirements are on the upper end of what is recommended, choose the next largest chiller to ensure an adequately cooled aquarium and healthy inhabitants. For example, if you have a tank size of 225 gallons and you need an estimated pull-down of 15°F, the 1/5 and 1/4 horsepower units would be too small; you would need a 1/3 hp unit. Some expert aquarists recommend to always get an over-sized chiller since it may save on electricity by not needing to run as long.
In the better models of chillers, the heat exchanger and compressor are held rigidly together, NOT with a flexible connection. The two metals most commonly used in the heat exchanger are titanium, and Teflon-coated copper. Titanium is expensive and is not a good conductor of heat, however, it is impervious to the saltwater that can corrode many other types of metal. When using coated copper, routinely perform a visual inspection of the unit. Any crack in the coating can expose the copper to the saltwater and result in increased copper levels in the water, with possible toxicity and death of the inhabitants.
