NANFA-L-- Chlorine

Subject: NANFA-L-- Chlorine
From: Hoover, Jan J ERDC-EL-MS (
Date: Mon Nov 29 2004 - 11:17:49 CST

Last week, after topping off three large (> 100 gal) tanks with tap water,
the fish in the first of the three tanks turned belly-up. Fish were saved
by immediately transferring them to other tanks. While doing water changes,
we noticed that water coming out of the tap had a stronger-than-usual odor
of chlorine. The total volume of water added to the tanks was small (< 15
gal), but we wondered if chlorine could have been the culprit. The incident
reminded me that I never have learned how dechlorination works. I wondered:

Are commercially-produced dechlorinators "sensitive" only to variation in
water volume and not concentration of chlorine ? Is the recommended dosage
(e.g., 1 drop per gallon, or 1 ml per gal) based on a presumed maximum
concentration of chlorine used in most municipal water systems ?

Do dechlorinators effectively neutralize chlorine when tap water is diluted
with aged water? For example, when making a 20 gal water change to a 60 gal
tank, should you add 20 gal worth of dechlorinator or 60 gal worth ?

Please excuse what may be naive questions from a chemistry- and
physics-impaired individual.


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: Fri Dec 31 2004 - 12:42:54 CST