Pearling after a water change

[Mike Wickham <mewickham at compuserve_com>]

Rachel,

 >> ...plants bubbling like crazy after a water change...

I missed the messages to which you refer, but I suspect what you are
describing is merely condensation of gases. Cold water holds more gas than
hot water. So when cold water passes through the water heater, it wants to
release some of its dissolved gases. But since the water is still contained
in a pressurized pipe, and pressurized water holds more gas than
unpressurized water, those excess gases have nowhere to go and stay
dissolved.

However, when the hot water is released from the tap, the pressure is
released. So those excess dissolved gases begin to condense out of solution
as microfine bubbles. (That's why a glass of hot water looks cloudy for a
short time.) The bubbles stick to plants and other surface and grow as more
condensing gases sticks to them-- which is probably the pearling that's
being described.

Pearling from condensed gases can be reduced or eliminated merely by
agitating freshly drawn water to "shake out" the excess gas. You can do
this by drawing water into a bucket first, letting the flow churn the water
heavily as the bucket fills, or by placing your thumb over the end of a
hose to force a jet of water to agitate the water surface as you fill your
aquarium. (Never stick the hose end under water as this will prevent the
excess gases from shaking out.)

If the pearling is from gas condensation, it's probably not good. It's said
that, before these gases condense out of solution, they are being absorbed
by the fish and can cause internal gas supersaturation problems, condensing
out of solution inside the fish-- the fish equivalent of the "bends" seen
by divers that surface too quickly.

Mike Wickham (mewickham at compuserve_com)