Define coldwater? What is the maximum temperature you want to keep?
I know the catalina goby does well in cool saltwater tanks. I believe the max temp for this fish is lower 70s.
Well, I use the term "coldwater" out of convention, really. It truly is a relative, if not useless, term. "Temperate" is most appropriate, technically, and doesn't even imply cold but, rather, moderate temperature ("polar" is cold, but again, it's relative-- a polar organism would say those waters are
just right, and that temperate waters are
warm). To further complicate the issue, the terms temperate, tropical, etc. refer to latitude and not temperature. Latitude is, of course, a function of temperature, but we must remember that this doesn't relate to a particular temperature
value; for example, one may find very cold water indeed in the tropics at extreme depths, prevailing oceanic currents may bring warm waters to temperate or even polar environments, and so on. But, putting all of that aside, temperate temperatures usually fall between the mid-40's to the mid-60's. Most species from these habitats can be successfully maintained in aquaria at temps in the upper 50's. You offer an interesting example in the case of the catalina gobies, which are usually said to occur in temperate waters-- though, technically speaking, they are really subtropical.
