Originally posted by RTR
ewok - just curiostity, but why would you use heaters if you knew they served no purpose?
rtr: the obvious, avoid temperature fluctuations at all. my few experiences with ich have all come with colder temperatures, this is an old house.... why risk it? for the $30 or $40 i paid for the heaters they are cheap insurance too, in case of whatever happens. it doesn't cost anything besides intitial investment if they never run and i doubt they will wear out like that. i like those fish down there and they wouldn't be there if i could keep them in the normal areas.... not to mention there is the off chance of furnace failure or other unknown problems.....
wetman: there is no substantial heat source down there, the temperature is strictly radiated heat from the furnace and heating pipes. maybe some slight heat from the freezer and gas refrigerator. it is not cold and has never been, but the possibilty still exists and there are no direct radiators in there at all. 2x 250 is only500 watts...... on a 90g with high circulation..... it's only a little more than 5 wpg.
i also remember reading somewhere, that raising the tank temperature above the ambient temperature is more on a curve. the higher above ambient the more watts you need. there is a threshold value, something like 10 degrees above ambient temp, that anything above that point actually starts to require massive watts....... i think it had to do with the amount of surface area for radiated heat loss, after a certain point the tank actually begins to heat the surroundings like say a radiator for your furnace. so take for example say 60 to 70 degrees, it is very easy and requires few watts, but 50 to 70 would be different, and not be twice the watts (for 60 to 70) like you might expect, but more like 5 x the watts............ this may be total bull, but i think i remember seeing this referenced in a couple of places when i was doing research on heaters and the concept made sense to me.
i also think that by having big heaters they do not work as hard, and this would be a cause for premature failure. (working too hard) if they can stay on for 5 minutes and do the job and shut down and cool off, it is alot less wear and tear than taking 1/2 hour for the same job. metals and other substances have a "finite" life and will only tolerate certain things for certain amounts of time, take the heating coils for example... they heat they expand they shut off they cool and contract.... over time the metal will become brittle and eventually that would cause failure.
if you'd like i could find my references i think still regarding the watts per gallon and ambient temperature. the premature failure theory is just that, conjecture based on fact, but i am sure i can reference metal failure rates also...........