Foam or no foam? (between tank and stand)

[Anonymous]

I am having a 330g glass tank built (96" x 27"). The tank will have a plastic frame on the bottom perimeter. The builder is also welding me a 2" tubular steel stand. I plan to glue a sheet of 3/4" plywood to the top of the steel stand on which the tank will sit.

The builder recommends that I place foam between the plywood and the bottom of the tank. That said that the foam would compensate for any changes in the "flatness" of the stand that might occur due to settlements in the floor (reinforced concrete - commercial highrise), particularly since this is an 8' long tank.

Is this a good idea? Any downsides? And recommendations on the type of foam? By my calculations, the load on the foam will only be about 1 psi (assuming an even load distribution), so pretty much anything will probably work.

 

[Len]

I am going with no foam on my new tank, but i'll make sure to have it perfectly level (and my floor bottom has been reinforced and there's been a 120 gallon over it for a decade, so it's unlikely to contort anymore). I don't know if there is any problems with foams (none that I can think of). I'm just a "if it ain't broke, don't fix it" kind of guy, I guess My 120 gallon has no foam and isn't even perfectly level, and it's lasted a decade 8O

Most people I've seen use styro.

 

[Anonymous]

I don't think it would hurt... but don't think it would do anything either. The weight of a 330 gallon tank is pretty extreme for foam, no?

~wings~

 

[lobo42a]

When I lived in Hawaii I had a2in peice of styro sandwiched between 2 peices of 1/4 in lexon for my 300 gal reef tank.The stand was made of welded 2in square tubing. I used to dive and collect fish and inverts for a local wholesaler.

 

[Anonymous]

>...my floor bottom has been reinforced and there's been a 120 gallon over it for a decade, so it's unlikely to contort anymore...

I don't know, Len. Unless the legs of the stand is at the exact spot, the contorted floor will need to be re-contorted to adjust to your new setup.

>...The weight of a 330 gallon tank is pretty extreme for foam, no?

The weight maybe extreme, but for PSI aspect, it is pretty small. Think about your car's tire pressure. 30PSI to hold up all that weight. the foam can deal with several PSI, and give the large surface area between the tank's bottom (assume it is flat bottom without trim), it is not big of a deal. In fact, the foam won't change much even if you fill the tank up with water.

 

[Anonymous]

What is important to the foam is not the total weight but the height of the water above it. Higher the water the greater the pressure.

I have used foam when there is plywood covering the entire bottom. Just the builder's supply 1/2-3/4" foam insulation. It does help compensate for any unevenness in the stand.

My 'gut feel' is that without the foam, the tank bottom is held off the stand by the bottom plastic frame. That results in higher stress in the bottom glass as it bends. With the foam the glass is supported over its entire area instead of just at the edges. So it should reduce stresses in the glass and bending in the silicon sealant at the edges.

But then many many people use stands which support the tank only on the outside edge. And they seem to last for years that way.

Bob

 

[Len]

Tanks this size do not have outter trims. They have perfectly flat bottoms.

 

[Anonymous]

Thanks Len. I'm likewise not convined that it is necessary, and it will make it a lot tougher to put an 800 lb tank on top of the stand since the foam means I won't be able to slide it into position.

The stand will be placed on carpeting, and not directly on top of the concrete floor. I would guess that the carpet will take up any irregularities in the "flatness" of the floor. And even if the floor sags, I would assume that the stand is sufficiently rigid to avoid sagging it self (which would be very bad ). Hmmm. Any more thoughts?

 

[Anonymous]

Tanks this size do not have outter trims. They have perfectly flat bottoms.

I think that is correct. There is a plastic frame around the perimeter, but it is (I think) nothing more than an "L"-shaped piece of plastic with very little thickness.

 

[Anonymous]

What is important to the foam is not the total weight but the height of the water above it. Higher the water the greater the pressure.

I have used foam when there is plywood covering the entire bottom. Just the builder's supply 1/2-3/4" foam insulation. It does help compensate for any unevenness in the stand.

My 'gut feel' is that without the foam, the tank bottom is held off the stand by the bottom plastic frame. That results in higher stress in the bottom glass as it bends. With the foam the glass is supported over its entire area instead of just at the edges. So it should reduce stresses in the glass and bending in the silicon sealant at the edges.

But then many many people use stands which support the tank only on the outside edge. And they seem to last for years that way.

Bob

FWIW, I have a glass 360g and steel stand set-up from the same builder. I did not use any foam between the tank and the stand, and so far (3 years), no problem. But that tank has 1" thick glass and is not as long (78"). The new tank will be 3/4" thick glass.

 

[Len]

Hmmm. I'm only partially correct then

 

[Anonymous]

>...my floor bottom has been reinforced and there's been a 120 gallon over it for a decade, so it's unlikely to contort anymore...

I don't know, Len. Unless the legs of the stand is at the exact spot, the contorted floor will need to be re-contorted to adjust to your new setup.

>...The weight of a 330 gallon tank is pretty extreme for foam, no?

The weight maybe extreme, but for PSI aspect, it is pretty small. Think about your car's tire pressure. 30PSI to hold up all that weight. the foam can deal with several PSI, and give the large surface area between the tank's bottom (assume it is flat bottom without trim), it is not big of a deal. In fact, the foam won't change much even if you fill the tank up with water.

The plan dimension of the tank is 96 x 27 = 2592 sq in
The tank probably weighs 800#
The weight of the water is 8# x 330g = 2640#
Sand and rock probably add another 400# (net)

So, that is [800 + 2640 + 400] / 2592 = ~1.5 psi. of tank bottom.

It would seem that most any high density foam would be able to handle this with minimal compression.

 

[Anonymous]

Hmmm. I'm only partially correct then

And I was only partially incorrect :lol:

thanks for the info. My tank is not that large.

Moving that large a tank onto foam is a problem and a good consideration.

 

[Anonymous]

Hmmm. I am leaning towards using the foam since I don't see how it can hurt. I will have to swing by HD to see what kinds of foam that sell and look for something that will have some (but not a lot) compression under a load of 2-3 psi. This should allow for greater compression in isolated areas of increased loading that might result from warping or sagging of the stand.

 

[Anonymous]

I think you will find the same pressure under any sized tank with the same vertical measurement. Just the way it works.

 

[Tackett]

WATCH OUT putting the thing on carpet dude. If I were you I would cut a hole out of the carpet to put the tank stand. Be very careful with carpet.

 

[Anonymous]

>...Thanks Len. I'm likewise not convined that it is necessary, and it will make it a lot tougher to put an 800 lb tank on top of the stand since the foam means I won't be able to slide it into position. ...

I know you had changed your mind since the sentence above, but even with foam (styrafoam), you can still slide an empty tank on it.

 

[Anonymous]

WATCH OUT putting the thing on carpet dude. If I were you I would cut a hole out of the carpet to put the tank stand. Be very careful with carpet.

Why the concern?

 

[Anonymous]

>...Thanks Len. I'm likewise not convined that it is necessary, and it will make it a lot tougher to put an 800 lb tank on top of the stand since the foam means I won't be able to slide it into position. ...

I know you had changed your mind since the sentence above, but even with foam (styrafoam), you can still slide an empty tank on it.

My concern was that sliding the tank into position would probably mess up the foam.

 

[Anonymous]

Ghost I think Tackett is concerned about the padding under the carpet compressing. I would also worry about any foam under the tank becoming compressed unevenly but I am not sure how thick we are talking.