On Fri, 23 Sep 2005 21:10:33 -0400, "David C. Stone"
wrote:

In article , Dr Engelbert Buxbaum
wrote:

fish lover wrote:

Anyone knows a good PH monitor? I don't like the strips and don't want
to pay too much.

The cheapest option probably are the pen-shaped portable ones, where the
electrode and the instrument form a single, small unit. Precission is
limited, but more than sufficient for aquaristic purposes. Lab supply
companies sell them for about 50-70 US$. Only disadvantage: they run on
button-cells, which don't last long and are quite expensive.

Remember that you need to keep the electrode in storage solution when
not in use. Never allow it to dry out, as it would become busted. You
also need calibration buffers (usually pH 4 and pH 7).

You can probably get away with just the pH 7 for fish tank water - the
pen-style pH probes I've used in the past have only had a control
for setting the pH 7 point.

Two things to be aware of: the respose will probably be slow in fish
tank water, i.e. it will take a while for the reading to stabilise; and
there is the potential for what is known as "poisoning" of the sensing
membrane from dissolved amines (which hopefully remain at very low
levels if your tank is setup and maintained correctly.)

If possible, also look for a pH probe which does automatic temperature
compensation (ATC).

Thanks for the help. I'm going to try a pan-shaped ones.