Hi there. I have recently become interested in building a coldwater aquarium. I live in Alaska and would love to have a tank in my home/business that recreates some of the local marine ecosystem... flounder, crabs, rockfish, etc. I would have to work out what I could humanely include, who eats who, that sort of thing...

But my question is this: How do I go about maintaining a water temperature in a saltwater tank of about 50 degrees F? I've looked at chillers, but most seem to claim they can only reach a temperature of 60 degrees. How do I bring the temperature down even further (reliably)?

I'm a marine biologist so I know a fair bit about these creatures, but I'm kind of new to building/maintaining aquaria.

Thanks.

I found this site in a web search for aquarium coolers. Perhaps it is what you are looking for, or something similar.

Modified 1/5 HP Chiller

How cold is it outside , you could run it to an outside tank and when the tank water became 50 degrees a valve would open and cold go in and warm go out, just an Idea. Im sure you would have to have heaters on the lines and the tank to keep from freezing. That would be cheapest. lol
Ps for another cheap idea> a freezer set to say 38 degrees to cool quickest, a thermostat for valves opening wa la!!!! lol (your tank inside the freezer of course).