pH of reconstituted fresh water

Michael Lardelli mlardelli at
Fri Jul 10 09:42:09 EST 1998

Dear All,

I hope that you will be able to give me a little technical advice on
maintenance of pH for zebrafish culture.

To ensure water quality in our recirculating system we prepare our water by
addition of aquarium salts to deionised water. This is performed in a water
preparation tank by an automated system that gradually adds a concentrated
salt stock solution and monitors the resultant conductance. If this water
was simply deposited into the main system then the resultant pH of water in
the aquaria would be 5.5, so we correct this to 6.5 by addition of NaHCO3
in the concentrated salt stock (sodium bicarbonate).

The NaHCO3 addition is not a robust procedure - it seems that small
variations in the amount of NaHCO3 added can give considerable variation in
the pH. I wonder if anyone knows of a better buffering system to use. I
have seen that some aquarium shops sell a buffer system called "Bullseye
6.5" although the cost to us for the volumes that we need would be
prohibitive. The ingredients are not listed on the bottle so we cannot copy
it. I note also that Aquatic Eco-Systems Inc. sell "pH stabilizers" but I
have no experience of their use and I imagine that the cost would still be
too high.

Does anyone know of a better buffering system that we could use or how we
can correct our low pH? I would be very grateful for any advice!



Michael Lardelli
Department of Genetics
University of Adelaide
South Australia, 5005

Tel.    (Aust. = 61) (0)8 8303 3212  direct
        (Aust. = 61) (0)8 8303 5633  departmental secretary
Fax.    (Aust. = 61) (0)8 8303 4399
e-mail. mlardelli at

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