04-15-2010, 01:21 PM
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Here is a good, well-referenced, objective mythbuster from aquariacentral on why (reasonably) high temperatures have been confirmed to be undetrimental (and somewhat beneficial) to goldfish health: Myths About Goldfish and their Care
An excerpt from Fancy Goldfish
: Care and Collecting by Richard E. Hess and Erik L. Johnson:
The temperature at which we should house our goldfish collections is the subject of debate. While it's true that goldfish of most varieties are extremely adaptable to a wide range of temperatures, there is considerable evidence that goldfish do best in water in the mid to high seventies. This temperature range has several clear advantages. |
First, it ensures that the water still carries sufficient oxygen. Water warmer than this carries far less oxygen.
Temperatures in the seventies also ensure adequate function of the nitrifying bacteria in the biological filter. Colder temperatures jeopardize the efficiency and capability of the nitrogen cycle.
Since goldfish are "cold-blooded" animals (poikilotherms), this temperature range ensures the proper functioning of fish metabolism and normal levels of activity without unduly increasing their oxygen demand. Different varieties of Goldfish also demonstrate different degrees of adaptability to temperature. The hardiest varieties, including Comets, Shubunkins, and Wakins, will survive winter in North America unless the pond freezes solid. The more highly selected varieties such as Orandas, Ryukins, and Ranchus may survive a temperate winter in North America when left outside, but in my experience they do this with less and less success as they mature. For further discussion of temperature, see Chapter 5.
From This online excerpt form the book
I find that higher temps (my guys are kept at 76) increase the speed at which the bacteria break down ammonia and nitrite, not to mention it accomodates the temp preferences of most plants which aid in the reduction of nitrite. The fish are also less lethargic and more active. Furthermore my tank is at a constant temperature when controlled by the heater so I don't have to worry about stressing the fish out with heat goes off at night.
Plus, if you are filtering your tank adequately (10x the tank volume in GPH) there is no reason for a temp in the 70s to compromise dissolved oxygen.
I believe Lupin is on the heater bandwagon, perhaps he will offer his thoughts?