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RE: [APD] aquarium stand level

Candy writes:

> I have read through the archives about leveling a tank using shims etc.
> question is how much out of level warrants pulling a 55 gal 48" long tank 
> apart to re-level it. The tank is at a friends house and has been up
about 2 
> months. When visiting her I noticed that the water level showed on one
> The difference is 1/4 inch or less (based on air space showing above the 
> water level at one end) along the 48" length of the tank. She is living
> an older house and had leveled it with shims however it is still out of 
> level as above. She has it on a "Wal-Mart" wooden stand that touches the 
> floor at both ends and in the center. Is this enough variance to take it 
> down and redo it or am I just paranoid like she says?

In my experience, the tank can be out of level by any amount. It is not the
leveling of the tank that is important although it looks better if it is
level, that is, perpendicular to the force of gravity, because you don't
see a gap between the waterline at one end (or side) of the tank while it
appears full at the other. This is similar to a picture hanging on a wall;
it is distracting if it is hanging crooked but it doesn't damage it in any
way.  What is important is to eliminate the amount of twisting force or any
point source loading on the tank. These forces can easily break the glass
or cause leaks. Checking for this can be done if the tank is full (as in
your case) but is better done without incident before you fill it. In your
case the tank is full, so lets go from there.

How can you tell if the tank has any twisting force (a bad thing) applied
to it? This can be done by looking at the tank. Looking at the ends (short
sides) of the tank first: Adjust the water level in the tank so that it is
just at or slightly below the bottom of the trim at one end. Is it level?
-- maybe, maybe not, but note its relationship to the trim along the width
of that end of the tank. Now look at the opposite end of the tank.
Specifically, look at the water line. What you are looking for is to see if
the water lines have the same relationship to the trim at opposite ends of
the tank. For example, If the water line at one end makes the tank appear
to be tilted slightly in one direction (forward or backward) or level (no
evidence of tilting forward or backward) then the water line at the
opposite end of the tank should indicate the same thing, in the same
amount, in the same direction, even though it will be higher or lower if
the tank is not level from end-to-end. If the tank is not level then adjust
the water level against the trim height (like you did at the other end) so
you can make a comparison. If they are different then the tank has a twist
in it, or possibly the trim was put on the tank crooked. I would
investigate the twisting possibility very thoroughly. If you suspect that
the tank is twisted then drain it before you make any adjustments; but you
already knew that. Of course you could just use a carpenters level if you
have one or can borrow one. Set it across the top frame at either end of
the tank. The location of the bubble in the vial should appear identical
for the reading at either end of the tank.

Now, about point source loading: The tank must sit on a "flat" surface.
Flat does not mean level, it just means no curvature in any direction. The
tank stand you have may (or may not) be level but it had better be flat. If
the tank is not sitting flat but some corner of the stand is slightly
higher or lower than another then this will cause a twist, as was discussed
above. If there is a high spot anywhere along the length of the sides then
this will cause a lot of pressure at one point on the tank. The weight of
the tank should be evenly distributed along the bottom frame (of a glass
framed tank). The worst case would be a high spot in the middle of the long
side of the tank. If the tank was empty you could check for this by seeing
if it would rock it slightly from end-to-end. If the tank does not sit in a
recessed stand then you can visually check to see if it makes contact all
along the base by trying to slide a thick piece of paper or credit card
under it at various points along the base.  In the case of a full tank,
either the weight of it may be enough to flatten the support, a risky
assumption, or the glass might break if you guessed wrong. Better to check
for this while the tank is empty. I mention point source loading, the high
spot problem, because you said the stand is on an uneven floor supported at
both ends and in the middle. If the stand is cheap enough, that is, if its
made of thin particle board, then an uneven floor with a high spot in the
middle could cause the stand to flex and assume the same characteristic as
the floor creating a high spot and an uneven distribution of the tank
weight. This is probably the most unlikely worst case scenario but it is
possible and aquariums have been broken this way. More often they spring a
leak from being set up on a non-flat stand which causes a twist. It is
better for the tank (glass tanks) to be supported at the ends with the
middle not having any support than too much support in the middle and not
enough at the ends.

Now, with all that said, your friend's tank is probably just fine as it
sits even though its slightly out of level. I would just check to make sure
there is no twist in the tank and that its not sitting on a big hump in the
floor. Check the shims. If any appear loose then that is an indication of
trouble brewing. My fish room is an enclosed patio. It used to be an open
patio but it developed a leak in the condo below us when it rained so they
(previous owners) closed it in. The floor is sloped to allow drainage of
rainwater and all my tanks sit out of level but I make sure when I set one
up that it is evenly supported along the bottom frame; that is, the support
surface is flat or planar. Wether the tank sits on the floor or on a stand,
somewhere between the tank and the floor there is some kind of stress
relief material to ensure any irregularities I may have missed are absorbed
and that the tank is supported as uniformly as possible. The material I use
depends on if I care what it looks like and if I need thermal insulation.
Some materials I have used for this are: felt weatherstripping, cut-out
pieces of Styrofoam produce trays that meat or fish come packaged with,
1/8" closed cell foam, rigid building insulation such as Styrofoam or
urethane foam, carpet, and cork tiles. Well, a long post in response but I
hope it helps prevent a disaster.    


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