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Re: Deposits on Glass

>I know these well, and I have turned to this list for help in the past,
>getting a lot of responses.  It took me a while to convince people that
>these deposits are not calcium.  What they are is silica deposits that come
>from water condensing on the bottom of the glass when the light is off and
>then drying up when the light is on and the glass is heated.  Each time the
>water condenses on the glass it dissolves some of the silica, and each time
>it dries up, it redeposits it.  After a year or so of this process
>happening every day, you get very clouded glass.  You can probably see
>round spots on the glass that correspond to the locations of the drops that
>form there every night.

A few years ago, when I had a glass tank, I constantly had these same
annoying deposits appearing on my glass top.  No matter what I tried, I
couldn't remove them completely, and I went through several glass tops.
Then I switched to an acrylic tank and have never seen these deposits again.
This makes me think that one and/or two things are at play here: 1). These
deposits don't stick to acrylic, or 2). The amount of deposits depends on
how closed your system is, and constant high-humidity levels prevents the
deposits.  My acrylic tank is almost completely closed.  The only openings
are at the rear of the tank over the enclosed filtration system and a small
24" x 6" opening in the top front of the tank.  The rear openings are
completely covered with black ABS fittings and the front opening is covered
with a flat sheet of Plexiglas.  I experience almost zero evaporation with
this tank.  When I look at the top of the tank in the morning, the underside
is completely coated with condensation, but it goes away after the lights
have been on for about 30 minutes without leaving any deposits.  Maybe the
encapsulated humidity prevents the deposits from appearing?  I don't know.
Maybe someone else here knows.  I realize this post doesn't answer your
question, but it does give another interesting observation about the
differences in equipment.  I suppose you could always switch to an acrylic
tank if the deposits are unbearable, but then you eventually have to deal
with all the God-awful scratches in your tank walls.  It's a nasty
trade-off.  In fact, after Christmas I will be switching back to an
All-Glass aquarium just because I can't stand how easily acrylic scratches.
Therefore, I will wait for the responses on how to remove the unsightly
glass deposits I know I am going to have to deal with again!


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