I think most fish can take a tremendous amount of variance in their water
temp. I know 10 degrees F is acceptable... I'd not put 20 degrees + out of
the question. From quick flashes from a cold rain, to water bursting out of
the mountains, even to the different currents that ocean fish experience.
Small stream pools can change temp quickly overnight or with a cold rain. Or
see how many fish are running in and out of a main system and a much colder
tributary's waters. I've had patches of water hit me in the stream that
have made me just shudder. I'd say they're enjoying the temp change, if
not, the higher DO2 and possibly better foods :)
And it's just not freshwater... If you've ever gone into the ocean, you know
for sure it's not an even temp, especially when tides are pulling water in
or out. One case example that screams at me was this salt pond in the Keys
where Andy Borgia showed me the way to some F. similis and F. grandis, with
other more typical marine species like half-beaks in the mix. The water in
the pond was hot from baking at low tide, but we were there as the tide was
coming in. These fish were swimming out of water that had to be in the
upper 80's (I broke from the action to get an idea of the temp of the pond
water). The water coming in was in the mid to lower 70's and they were
<Ahem> gettin' jiggy in it ;) There really wasn't anywhere for them to
adjust to the temp.
Certainly, this isn't a reflection of _all_ fishes. Switch a couple degrees
on a discus and you just ate $65.
What I think the _majority_ can't handle is environmental stresses they're
receiving in an aquarium (nitrate, poor diet, electricity, extremes in pH
compared to their preference), and then a swift temp change is just the
straw that broke the camel's back... And is probably the easiest to
observe, so it ends up a common "culprit".
Don't even start me on coral.... ;)
----- Original Message -----
From: "Ty Hall" <tyhall_at_mia.net>
Sent: Saturday, October 25, 2003 10:12 AM
Subject: Re: NANFA-- Temps
> I think in a lot of cases it's not so much the overall temperature as it
> quickly the temperature of the water changes. If a tank is cooled or
> slowly, then the fish have a chance to adapt. If it changes quickly, then
> do not adapt and can and become weak. Which leads to illness and death.
> It's the same with us warm blooded types. Take a 50 degree day in
> are running around with no coats, thinking it's warm. The same temp in
> everyone is wearing a coat complaining about the cold.
> The way I explain it to most people is that the heaters in their tanks
> there as much to heat the water as they are to stabilize the temp and
> sudden changes.
> I agree with you Moon, that most homes are plenty warm to suit the average
> "tropical" fish. But given the small size of a typical home aquarium
> the fact that the temp in a house can have a 10+ degree range over the
course of a
> 24 hour period, you can quickly see how this rapid warm/cold cycle can
> fish. For more sensitive fish, this can quickly spell death. Even hardier
> will have a greatly shortened life span. A larger tank can lessen the
> the temp change as it does not change as fast as a smaller one.
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