[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

pH mythology.

There have been a number of panicky notes to the digest, recently, worrying
about pH change hurting fish. Those folks should relax a bit, IMO. Look

Much of aquaria chemistry has been messed up by confused authors and poor
translations, Perhaps nowhere is the gospel more deeply entrenched than in
the area of pH-change damaging fish. Well folks, it doesn't. Really!

I can abruptly change the pH of the water of very delicate fish by as much
as two full points and cannot observe any alteration in their behaviour.
Others have reported more than three points (1000:1 sudden change in proton
concentration) with absolutely *no* ill effects. See Scheel's _Atlas of
Killifishes..._, TFH, for example.

In the general range of 4 to 10, most fish probably cannot feel the pH by
any known sensory mechanism. Rapid changes of pH often have been blamed for
what was really tds-change-damage or nitrite/ammonia toxicity.

Hard water frequently has a higher pH than distilled or de-ionized water. If
you dump fish into the softer water, the pH sure does drop, and the fish
most certainly die. Works every time. The cause is the change in osmotic
pressure that bursts cells in skin and gills before the regulating
mechanisms can react. pH has nothing to do with it.

If you have a lot of ammonium (harmless) in solution, a sudden rise in pH
will release copious amounts of deadly ammonia as the equilibrium condition
changes. Less common is the increase in toxicity of nitrites at *lowered* pH
(<5 or 6).

In heavily-planted tanks with lots of photosynthesis/respiration, ammonia
and nitrite are really hard to detect. pH changes under the circumstances
should have no effect at all on fish.

There are a few, rare, pH-related effects seen in breeding wild rainforest
fishes, but I suggest the concerns expressed here should be directed toward
changes in osmicity and nitrogen-compound toxicity problems. The pH itself
is not the cause of fish distress. [Even in those rare cases mentioned, it
is usually calcium ions that disrupt the breeding process or eggs and not pH

pH changes don't hurt fish. Osmicity changes need to be gradual, to allow
the regulation to adjust. If you have ammonium/ammonia, slow change will be
every bit as deadly as quick change of pH.

Since I'm attacking some emotionally-held "faith," guess I had better raise
my flame shield, now. (^_^)


Wright Huntley, Fremont CA, USA, 510 494-8679  huntleyone at home dot com

         "DEMOCRACY" is two wolves and a lamb voting on lunch.
     "LIBERTY" is a well-armed lamb denying enforcement of the vote.
             *** http://www.self-gov.org/index.html ***