More musing on water change.

[Wright Huntley <jwwiii at pacbell_net>]

There seem to be two opposite schools on how much water to change at any 
one time. Charles uses the toilet flush analogy to argue for as close to 
100% change as practical. Most medications, books and others on the list 
advocate 25% change at each water change.

I'd like to toss in my US$0.02 on what these mean and why they come about.

For a while, I bred Bettas, both ornaments and wild species. It is 
common practice to do 100% water changes on the small jars used to house 
growing male Bettas, and similar amounts on bigger tanks of growing fry 
or females.

In order to do that, the Betta breeders had gone to chemically-treated 
water, using hypo as the preferred dechlorinator (or the expensive LFS 
dilutions thereof). As the EPA worked down the chain of municipal 
suppliers, requiring the change to chloramine, a couple of the best 
breeders (both held the "Grand Champion" title at the IBC, BTW) missed 
the announcement of the change, and were dismayed when they just wiped 
out their entire fishroom in one day. We're talking thousands of fish 
and many selling at over $100/pr.!

A serious water-department overdose of chloramine (>2.5 ppm in one case) 
combined with the hypo-caused release of ammonium into moderately 
alkaline tap water was enough to kill almost all their fish. [The EPA 
was simultaneously trying to protect folks from lead poisoning by 
forcing water pH to a bit over 8.]

These two incidents happened in the deep south and southern CA at nearly 
the same time. Many, many other similar stories have come to my 
attention, not only with Bettas but with killies and chicklets. Most 
were a bit less disastrous, but the results were close to as bad in many.

The wipeouts were an extreme case that required simultaneous bad factors 
to all be present. The 100% water change was the only one the breeder 
had any control over (barring filters, etc.).

If the normal 1-2ppm of chlorine is present in your tap water, the fish 
will show very little distress when 25% of the water is changed with it 
after it has just stood long enough to reach room temperature and 
outgas. [No dechlor product is needed, but aging with aeration overnight 
completely removes the chlorine.]

Add an old-style dechlor agent (hypo), when there is chloramine at 1 
ppm, and the released ammonia will still be below distress levels in 
most cases, but will cause some stunting and gill-filament clubbing in 
babies. The fish may briefly gasp below the surface to get more oxygen, 
but otherwise seem to recover quickly if only 25% is changed. This is 
*not* good for your fish at all, but also avoids complete disaster.

Here are my conclusions:

25% water changes are safer if you have chlorine (untreated) but are 
questionable if you have much chloramine. Chemical treatment is always a 
good idea unless your water is known to contain no toxins at all.

100% changes do the cleansing job best but carry much higher risk of 
catastrophe if your water has changed in ways you don't understand.

In addition to variables in chlorine/chloramine, many districts use 
water from multiple sources, so pH and tds may change on you with little 
notice. Our Palo Alto water, back in the '50s, used to drop from well 
over 300ppm to less than 50 on Mondays as they added SF (Hetch Hetchy) 
water to that from the local wells after weekend-lawn-watering drained 
the local supply.

A 100% water change on Monday could have been a disaster, even though we 
had no chlorine in those days.

If you have good control of your source water (e.g., by correct 
filtration) or are a good chemist, like Charles H., then 100% changes 
are pretty safe.

If you use "Prime," "Amquel," o/e and do 100% changes you are safe from 
chloramine/chlorine, but still must guard against tds shock.

In general, I think sufficiently-frequent (weekly?) 25% water changes 
will remove enough waste products to do the job and still avoid the 
worst of the disaster scenarios. Still use your dechloraminator or 
dechlorinator, as appropriate for your water. No pH or tds variation 
will be a bother at 25% change, where it could be deadly at 100%. Even 
moderate temperature differences (5-10 degrees?) will not bring on a 
Velvet or Ich outbreak at 25%.

Guess I better go find my asbestos suit so Charles can respond. :-)

Wright

-- 
Wright Huntley -- 209 521-0557 -- 731 Loletta Ave, Modesto CA 95351

"The right of self-government does not comprehend the government of others."
                                 -- Thos. Jefferson --

That's what Independence Day is all about, isn't it? <www.self-gov.org>


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