Re: [AGA Member] Re: Aga Members List

["S. Hieber" <shieber@yahoo.com>]

If you think part or your original frame is missing or
broken, or one of the joints is not holding properly, or
the glass seems to deflect just too darn much, then lower
the water level to reduce the strain until you can check it
out.  Call the manufacturer if you can or outfit that sold
you the tank.

Better safe than wet, and better safe than cut.

The glass or acrylic panels of aquaria deflect; the answer
is yes, they bend.

With small Glass panels, the deflection is virtually
unnoticeable until you place a genuine straight edge up
agasint it. In a 20, you can eyeball if if you view
carefully down the front panel.  On a 30 and larger, it's
easier to see.  It's anticipated in the design of the
tanks.  Glass can deflect without breaking, but only just
so much.  The other panels and the joints help to constrain
the deflection.  the upper and lower plastic frames on most
modern glass tanks help hold the joints together and the
joint hold the panels and the panels help hold each other
in shape.


The same is true for acrylic except that acrylic also
absorbs water (not much but some), so one side of an
arcrylic aquarium panel will swell while the other doesn't,
which creates some harmless warp.  The tendency to warp is
constrained by the other panels and the joints hold them
together.  If you place a sheet of acrylic over a tank of
water and come back a 1/2 day or so later, you'll see
significant warpage.  As soon as the acrylic dries out, it
returns to flat.  This is why acylic makes a poor choice
for a tank cover, other things being equal.  However, the
thicker it is, the less it will warp.  But the thick stuff
is usually much more expensive than glass.  

Acrylic can defelcdt without cracking but only just so
much.

Polycarbonate can deflect entirely in half back on itself
and not crack -- that's an amazing property for a rigid
material.  But it's very expensive compared to plain
acrylic and the ability to deflect great amounts is not an
advantage for most aquariums, where very little defelction
is needed for the design or just using thicker panels will
make a big difference.

Oh, technically, glass too has some absortion factor, but
it is so miniscule that for most purposes, one can ignore
it.

Scott H.

--- Dennis Sheridan <dilvish@pacbell.net> wrote:
> From: "Kate Breimayer" <kate@munat.com>
> 
> > anymore! Do all tanks bend? Seems like most of mine do.
> It scares me.
> 
> heh.. None of my 3 do..  at least not that I can tell. 
> That would be scary.
> 
> d


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