pH and Conductivity of water

Peter Cattin p.cattin at
Mon Jan 13 17:00:40 EST 2003

Dear Christina,

I have been following your questions over the past few weeks and 
have responded to one of them regarding the appearance of fungus 
in your AHAB system.  Your last question on pH and conductivity 
provides clarity to some of your earlier points and problems.  

David Lains comments on the personal nature of water quality is 
correct but of course the fish have to agree with you and I am sure 
that is what David meant in his response.  My preference is for pH 
7.2 - 7.5, conductivity around 300 - 400 and temperature about 7.65 
- 7.8. Stability of water is at least as important as arbitrary 
preferences. Our fish are long living and fecund and that is all we 
want from them.  

But to put this last question of yours into the context of your other 
questions, I would strongly suggest you take all of the tanks out of 
your system and thoroughly clean them in very hot water and with 
a scrubbing brush.   Maintain your recently adopted decision to 
reduce the of dry feed and increase the quantity of Artemia fed.   
One feed of each a day will be heaps.  Don't feed more than the 
fish can consume in 60 - 90 seconds.  

The fungus will be there because of overfeeding and under cleaning. 
The tanks need to be physically cleaned about once a month or 

The next step is to increase the conductivity of your water.   You 
must be putting a lot of RO or distilled water into your system to 
get the low conductivity you have. The water can't be stable or 
"healthy" with this quality of water.  I imagine your response to the 
fungus has been to add more and more pure water more frequently. 
 Change about 10-15% per week and maintain the conductivity at a 
higher level.  To do this don't simply throw calcium and magnesium 
carbonates at the water as this will make it too hard.  Rather, 
reduce the amount and/or purity of the water you are adding.  

Hope this helps.


Peter Cattin
Peter Cattin PhD
Department of Molecular Medicine & Pathology
Faculty of Medical and Health Sciences
The University of Auckland
Park Road, Grafton, Auckland.
Private Bag 92019, Auckland,
New Zealand

Tel: +64-9-373-7599 xtn. 86373 or 87719
Fax: +64-9-373-7492

Christina Quasarano wrote:

> Hello everyone,
> I just have another quick question.  This is about the pH and
> Conductivity of the water in the tank system.  Out water is at a pH
> of ~7.3 and a conductivity range of ~130-150 microns.  I have been
> told that a lower pH (~6.5-7.0) and conductivity range at 300-500
> microns.  Which is the correct?  What do others use?  Any info can
> help! Thanks!
> Sincerely, Christina Q
> ***************************************
> Christina Quasarano
> Research Assistant,
> Chemical Hygiene Officer
> Department of Anatomy and Neurobiology
> Phone # (617)638-4187
> ---

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