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pH Probe Algae Protection

	I envy people who can put their pH probe in a nice dark sump, with
freshly filtered water pouring by it.  Mine goes in the tank, a few
inches from the lights.  Basically, it hangs in a 7" piece of PVC (or
ABS, or whatever that dark gray plastic pipe is.)  There's a 2" diameter
hole in the acrylic that goes across the top of the tank, to accommodate
heaters and syphons and such.  I took a piece of plastic pipe with an
outside diameter of about 2" and put it down the hole.  At the top of
this pipe I put a threaded plastic collar that keeps it from falling
into the tank. I drilled two 3/16" holes in the tube, one about 2" above
the bottom and one about 4" (at roughly the water line), so the water
can move around inside the tube a little.  These 2 small holes are
turned towards the back of the tank, away from the light.  Finally, I
made a sleeve out of black plastic door screen material that fits
loosely inside the tube and around the probe.  (I stitched this
screening tube closed with polyester thread, then put a couple of dabs
of silicone tank sealant to secure it in place.)  This keeps everything
bigger than about a millimeter out of the tube, while still allowing
water circulation around the tip.
	This was a crude solution that I just threw together, thinking I'd do
something better eventually, but every time I pull the probe out, it
looks brand new, so for now I'm just going to leave it.  Because it's a
dark color, in the corner, and getting an algae coating, it's fairly
visually unobtrusive.  
	I can't resist adding that hiding behind this plastic tube is a 1/4" x
3" stainless steel bolt.  Two stainless steel nuts above the water line
connect to a piece of wire that is in turn attached with a screw to the
metal case ground of the pH measuring circuit  This simple case ground
(which isn't even connected to the AC outlet's 3rd wire safety ground)
cut down on the amount of AC noise on the probe signal immensely!
-- Sherman Lovell