From: dphantom@triton.unm.edu (darlene an  92sep02 lawry)
Subject: Re: Boret Heaters
Date: Sat, 10 Oct 92 00:07:40 GMT
Organization: University of New Mexico, Albuquerque

>> Actually, that's not quite true...there are some hazards to using an
>> overrated heater.
>> 
>> 1)  It outputs more heat at one time, which for a very small tank, can
>> be a little stressful on the fish.  Relatively minor point in most cases,
>> but radical temperature changes are generally not a good thing to subject
>> fish to.
>> 
>I disagree.  If the water is well circulated, the temperature should not
>change so much so fast as to be a stress to the fish.  Even with poor
>circulation, I don't think the temperature changes would be "radical".

In a *two* gallon tank, to get enough circulation that the fish would have
no chance at being affected by 25 watt heater would be enough current to
kill the fish.  I said it was a relatively minor point...but it is one to
consider, if you have a fish that's not tolerant of temperature changes.  Experts recommend that you put "appropriately" rated heaters next to a place taht
receives good circulation to prevent such temperature change and for better heating in general...given this
advice, wouldn't it stand to reason that with an overated heater, this might
be even more of a problem?

>
>> 2) If your heater goes bad, you can toast your fish.  The object is to
>> have a heater that, if the sensor goes bad and it stays on, it won't cook
>> your fish.  I've had sensor's go bad on my heaters before, and I'd hate
>> to think if it had been in small tank.  Toastie poasties.
>> 
>Seems to me that if any heater goes bad your fish are toast....If a heater
>produces enough heat to maintain a warm tank temp when its operating
>properly, then if it sticks, it can toast your fish.

Actually, no, not if it's rated appropriately for the size of your tank. 
Here's a clip from an old (but good) book entitled, "Exotic Aquarium Fishes"
by William T. Innes, L.H.D. (still avaiable and in use today):

"A good general rule is 2 watts for raising each gallon 5 degrees above 
surronding temperature.  That is, if a 10 gallon tank is to be raised 5
degrees, use 20 watts.  For 10 degrees, 40 watts.  We favor conservative
sized heating units.  Then if a thermostat fails to function, the fishes 
are not likely to be "cooked"."
>
>> If you can't find a microheater, just use an incadescent light...should
>> do the trick.  Otherwise, you take your chances...
>
>Incandescent lights do keep the water warm...when they're on.  What do you
>do at night?  Seems that turning off the light will allow the water to cool
>and then need to be reheated the next morning,  this seems like a stressful
>situation, especially in a 2G tank which will change temperature rapidly.  
>The temperature fluctuations here would be much worse than any that might
>occur with an oversized heater.  Obvioulsly leaving the light on 24h a day
>would also be a big time stress.  

Obviously.  Like you said, a small heater would be the best answer...some
fish are not bothered by light, and can sleep through it just fine (well,
most if not all fish will sleep with the light on, actually...have a friend
that uses light to keep a betta warm in a bowl at night, hasn't had any
adverse affects on him yet, but I would still maintain that a heater would
be better, if possible).  Turning off the light at night is exactly what I 
am NOT suggesting...that's when it gets the coldest, and your fish would
suffer more stress (or death) from the cold than they would from leaving a
light on.  However, you're statement that the temp fluctuations would be
worse from the light than with an oversized heater (you used 25 watts in
your example), is entirely misleading.  Don't forget that your heater is in
direct contact with the water, while a bulb has to go through air, plastic,
and/or glass.  In the example I mentioned with the betta, the bulb being
used is a 100 watt incadescent, kept about 6 inches away from the bowl at
night.  The water does not get too warm (estimated 76 degrees early morning).
However, one must keep in mind that the place gets pretty cold at night
(not sure how cold, but the heating in the building is shut off).  It is left
on during the day, but kept farther away from the bowl.  For most purposes,
you may want to shut it off during the day entirely.


>
>I agree that a nifty little 7.5W heater would be the optimal choice, but
>I'd still rather use a good 25 watter than an incandescent bulb.
>
>Chris

It's your opinion...but I was also stating mine for the benefit of the 
original poster, so that he (she?) may decide for himself which would be
better, given his particular circumstances.

Xref: sparky rec.aquaria:8074 alt.aquaria:5371