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Re: dissolved oxygen and temperature

>In a message dated 97-09-24 01:03:18 EDT, Bob Dixon writes:
><<They are best kept chilled, but seem to di okay up to around
>76 degrees.  Above that and they do not usually get enough oxygen to survive
>(As temp rises, metabolic rate increases, and available dissolved oxygen
decreases). >>

Kevin responds:
>	Correct me if I am mistaken, but doesn't warm water hold MORE oxygen
>than cold water?  Is this not the reason that recommended stocking
>levels are lower for coldwater fish than for tropicals?  I can
>understand the metabolic rate of the fish going up with water
>temperature and coldwater fish not liking high temperatures, but this
seems "fishy"...;>

Kevin Murphy

Bob explains:

Water can disolve more of solids, such as sugar and salt when it gets warmer.
 Its capacity for dissolving gases increases as temperature goes down.
From my layman's point of view I understand the concept like this-
As the temperature of a dissolved solid goes up, it is harder for it to
solidify, because it is closer to its melting point.  Therefore the water can
hold more of it.
Conversely, as the temperature of a dissolved gas goes down, it is closer to
its condensation point, and this makes it easier for the water to hold it.
Is that clear?  The more I look at it the confuseder I get, but it is late
and I am overdue for bed.
Someone smarter than me can probably express the whole idea a lot better
anyhow, so I'm going to bed.