Foam under a SeaStar tank?

[The Grizz]

How would you support the bottom of the tank that has a couple hole's for returns so they don't crack from the hole????????

[christyf5]

bit of a late entry here but my 90gal was on a piece of that pink foam since about 2004 when I got it (and prior to that the 90 that I had was also on foam, probably that same piece, for a year). I'm not sure what kind of trim it had on it, probably the same as they always use. I noticed when moving the tank (twice) that the foam was compressed around the edges like you noted, Shelley, and figured that that was just the way it is. I was also told to use the foam, not from the seastar peeps though.

I stripped the trim off my current tank, I don't know who made it but the bottom trim was almost flush with the bottom of the tank, there was no "offset" of the trim and glass. Regardless, the trim is gone and the tank is sitting on a large chunk of foam....I think. Hmm, in hindsight maybe I didn't use any foam. Man my mind is mush lately, you'd think I'd know that

[StirCrazy]

now allot of this just doesn't make since at all... if your tank is a standard sea star tank there is about a 1/4 to 1/3" lift from the edge frame. if you are using 1/2" pink foam it will compress about 1/8th of an inch under load and the center glass should never touch the foam anyways. for the foam to cause a problem even if it is touching the center of the glass you would have to have a stand that is pretty far screwed up and not at all flat with weight on it.

there is one concept here that people are getting wrong, you have the exact same amount of weight (Pressure) pushing down on the whole bottom, weather it is in the middle or the edge.. pressure which is a force is influenced only by the the matter above it. I think the problem people have with foam is mostly caused by trimming it to close to the tank allowing the edge to collapse more than the middle, or thinking foam can adsorb more irregularity than it should.

the very edge will have the most weight as the density of the glass above it is higher than that of water so the edges should sink more. for instance I had a slight depresion in my foam around the edge like shelly's picture shows but the middle glass never touched the foam as pink won't compress that much

personally I think drilling the bottom would be a bigger cause of a break than it touching the foam as drilling a hole in it severely weakens the panel of glass thats why I always drill the back or sides of my tanks.

Steve

[PoonTang]

From the pictures it doesn't look like the center of the tank was touching the tank at all. Just discussing this with my brother in law who is a mechanical engineer. The foam is a good things it will distribute the weight over a larger area if the bottom actually touches the foam. You have either 1000 pounds pressing on 142" of frame or over 1142 square inches if the whole bottom. Having said that he said that foam is not always homogenous and could have had a high spot at any point under the tank that could have caused the failure. Or a cutting or manufacturing defect.

[StirCrazy]

one problem with your explanation here.. once the foam touches the glass then there will be less force on the edges and the trim will not be able to sink any farther, so in theory there is no way the foam can push up against the middle of the glass.. also judging by the picture I would say the middle of the glass wasn't even touching the foam. there are to many rough marks and such that would have all been smoothed out by any contact.

Steve

Originally Posted by Borderjumper

heres a picture I took of a piece of the foam we removed.. it may explain better than I can in typing.. see how the rim sunk into the foam all the way around, leaving the glass in contact with the foam. The farthur the rim goes into the foam.. the harder the glass presses into the foam.

[Dradee]

This Seastar tank has about a 1/8" lip on the bottom from the decorative trim which you can see from the picture of the pink insulation it sunk in about 1/8" all around the edge.

The stand top is level but the pink insulation I used was wavy and uneven BUT I thought it would flatten out and conform to the tank bottom but now looking it never really did. You can see in the pic of the foam that the scratches,nicks and dings in the foam did not even flatten out from a 1400lbs of weight.

This building insulation foam is very high density and does not want to conform at all. I also cut the foam totally flush with the tank after it had settled full of water/rock.

My theory is the pink insulation sunk in around the edges more pushing up in the center of the tank unevenlly putting a slight bending up force in spots now couple that with rock all down the middle, a wave maker and 16 months later, maybe even a slight flaw in the glass and it finally gave way and cracked.

I will never use this high density pink crap again! Weve had tanks for ever and always used low density foam carpet underlayment and it conforms very easily.

This is the product we used,Owens Corning FOAMULAR® 250 extruded polystyrene insulation
http://commercial.owenscorning.com/f...mular-250.aspx

Originally Posted by StirCrazy

now allot of this just doesn't make since at all... if your tank is a standard sea star tank there is about a 1/4 to 1/3" lift from the edge frame. if you are using 1/2" pink foam it will compress about 1/8th of an inch under load and the center glass should never touch the foam anyways. for the foam to cause a problem even if it is touching the center of the glass you would have to have a stand that is pretty far screwed up and not at all flat with weight on it.

there is one concept here that people are getting wrong, you have the exact same amount of weight (Pressure) pushing down on the whole bottom, weather it is in the middle or the edge.. pressure which is a force is influenced only by the the matter above it. I think the problem people have with foam is mostly caused by trimming it to close to the tank allowing the edge to collapse more than the middle, or thinking foam can adsorb more irregularity than it should.

the very edge will have the most weight as the density of the glass above it is higher than that of water so the edges should sink more. for instance I had a slight depresion in my foam around the edge like shelly's picture shows but the middle glass never touched the foam as pink won't compress that much

personally I think drilling the bottom would be a bigger cause of a break than it touching the foam as drilling a hole in it severely weakens the panel of glass thats why I always drill the back or sides of my tanks.

Steve

[StirCrazy]

Originally Posted by Dradee

This Seastar tank has about a 1/8" lip on the bottom from the decorative trim which you can see from the picture of the pink insulation it sunk in about 1/8" all around the edge.

The stand top is level but the pink insulation I used was wavy and uneven BUT I thought it would flatten out and conform to the tank bottom but now looking it never really did. You can see in the pic of the foam that the scratches,nicks and dings in the foam did not even flatten out from a 1400lbs of weight.

my seastar custom tank had a 1/4" lip under the edge, so they must be using a bunch of different bottom trims as I have seen a 1/2" raised one also.

I left my foam about 1/2" bigger than the edge of the tank so it wouldn't weaken the part the tank edge sat on. the problem with carpet underlay is it is not even and had hard lumps in it so it can be a very bad thing to have under there if the tank settles it down. I have never seen wavy pink corning foam and being homogenious it should compress evenly, but any foam thatr manages to allow the bottom to be suported has the same risks I guess. I just find it weird as sea star was the ones who told me to use that corning pink.

Steve