Foam under a SeaStar tank?

[Borderjumper]

My tank just cracked. The bottom cracked from one corner length wise in a big S all the way to the opposite corner.. For the full 4 feet.

This is.. Well was.. A 18 month old 4ftx2ft old Sea Star tank made with 1/2" glass.

We put a piece of pink insulating foam under the tank.

We just took the tank off of the stand and it looks like the edges of the tank compressed the foam slightly.

What Im wondering..if the edges compress, this is basically lowering the bottom glass until it contacts the foam. This foam is pretty rigid. I'm thinking that with the edges compressing, more pressure was being put on glass.

Looking at the bottom of the tank, it looks like the frame is slightly higher than the glass bottom.. But only a fraction.. I'm thinking the tank is made so that the edges carry all the weight and the bottom basically "floats" for a better word..

So if the glass is supposed to float, with no pressure on it from the stand are we screwing this up by letting the tank sink into the foam causing the bottom to make contact, which makes it suddenly bear weight?

Thoughts? And does anyone know if a seastar tank is designed so that only the frame carries weight? I remember tanks from when I was a kid.. They used to sit on those old metal stands that were only frames with nothing in the middle.


http://i6.photobucket.com/albums/y240/Carrida/IMG_0650.jpg

[Gooly001]

Hey Shelley,

Eugene and I had a discussion to find out how you achieved the crack on a 18 month old tank and we concur that it was the foam that may have caused the crack. Tanks with trims that leaves a gap underneath the tank and stand surface are designed to sit directly on the tank stand surface. If the trim is allowed to sit on foam, the slight difference in pressure may cause stress on the bottom pane and eventually crack. This is just our opinion but I would agree that the foam caused the crack.

Cheers,

Paul

[Mrfish55]

Could be an uneven stand causing the tank to twist, could also be a defect in the glass that just took that long to let go, I have seen a couple of virtually identical cracks and when the stand was checked for level, they were both found to have warped tops (both commercial stands) The foam underneath should not have made a difference, I as well as many others have used foam without issue. I don't know if Seastar has improved the build quality but I know the local shop quit carrying the line many years ago due to the failure rate. Hope you are able to get going again, you had a very nice setup, good luck and Merry Christmas.

[Aquattro]

Shelley, have you called SeaStar and asked them? Progressive has all their tanks on the same foam, I'd hate to see the store go pop!! I'm wondering if the wavemaker had anything to do with it?
My 90 is a SS but I had it on a foam underlay type of material. My 155 was also seastar and sat on foam for years.

[Borderjumper]

We will call seastar next week.. No one was answering today.

The foam theory does make sense to me. That pink foam has very little give to it...it's really quite hard, and the bottom of the glass was pressed into it pretty hard which is what held the glass together and slowed the drain down to a dull roar.

I've got foam under all my other tanks, but it's the much softer grey underlayment kind.. Not this rigid pink insulating foam.

the wavemaker I guess could have contributed... I sure would feel much better if I could pinpoint the cause.

[Aquattro]

I sure would feel much better if I could pinpoint the cause.

That's tough. Lots of people use foam, and lots use wave makers. The foam theory does make sense though. How much compression was there? Enough to force the contact between glass and foam? Thinking back, my 155 sat on a framed stand, no solid top so foam only contacted the edges. I never sit my tanks on a flat surface, so foam would work fine for me.

[Borderjumper]

Yeah the glass was defiantly sitting down onto the foam.. The edge of the tank had compacted down into the foam at least an 1/8 of an inch, putting the glass right on the foam,that's why the water didn't just gush..the foam was exerting pressure kind of holding it together. If a tank is not designed to have the glass carry any weight, and it's in contact with rigid foam.. It's carrying weight. If it woild have been soft foam.. Then I would think it would have just kinda of supported the glass.. Hard foam has no give.. So the glass was actually being pressed down on it..

Foam and the pink insulation foam may be two different things in this application?? Think of the foam floaties that corals come on.. It's hard and doesn't have much give.

[Aquattro]

Sounds like you've got your cause then. Still crappy!!

[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.

http://i6.photobucket.com/albums/y240/Carrida/IMG_0659.jpg

[imisky]

hey Shelley,

It was quite a shock when Paul told me about the tank, so as Paul has mentioned tanks with floating bottoms should only be supported by the trims and should never be put on foam in any situation. The result is usually what happened to your tank :sad: This is usually the case with tanks built with the 4 side panels sitting on top of the bottom glass. These shouldnt sit on foam as any pressure on the bottom will push onto glass that doesnt give much before snapping or in your case cracking.

Tanks thats built with the 4 side panels sitting around the bottom glass has a little bit of a flex if theres any pressure pushing up on it as the silicone holding the bottom panel to the 4 sides will flex as the bottom pannel gets pressure.

Hope that makes sense

Cheers,
Eugene

[Borderjumper]

Makes perfect sense but now my question is.. Have you ever taken apart a seastar tank? Is it a floating bottom? I can't tell without taking the trim off.

[imisky]

never taken apart a seastar tank before, but most (80% i would say) of the tanks I've taken apart with trims are infact built with the side panels sitting on the bottom panel. So there is a high chance that the seastars were built the same way.

[Borderjumper]

never taken apart a seastar tank before, but most (80% i would say) of the tanks I've taken apart with trims are infact built with the side panels sitting on the bottom panel. So there is a high chance that the seastars were built the same way.

I'm getting confused lol so tanks with trim are floating bottoms and should not be on foam? Or, It sounds to me that if the sides sit ON the bottom glass that the bottom is not floating?

[imisky]

haha ok, so tanks that have trims are all considered floating bottom.

out of all the tanks ive taken apart (AGA/Oceanic) majority of them were built with the side panels sitting on top of the bottom. That would explain why they needed the trim on the bottom.

In other words, most of the tanks built with 4 panels on top of the bottom are usually built with trims thus making them floating. The reason is because you are not supposed to support the whole bottom of tanks built this way only the perimeters of the base

[Aquattro]

Interesting, as I'm checking the bottom of my tank, I see it's leaking from somewhere above the foam. Gonna be an interesting Xmas morning for me!!

[MitchM]

Interesting, as I'm checking the bottom of my tank, I see it's leaking from somewhere above the foam. Gonna be an interesting Xmas morning for me!!

Oh, no!:(

Mitch

[StirCrazy]

I had my seastar tank on foam, and they were the ones who recommended it was put on foam and they even suggested pink.

now the biggest problem I see is if you are using a home made stand or even a pre-made stand on an uneven surface. once the foam is compressed it won't keep going so what happens is it will conform to the stand and transfer through any irregularities. it will make up for very slight ones but not for larger ones and they will eventually telescope through and have there effects.

I don't know if your stand was wood or metal but, I really hate it when I see people using wood to build frames for large tanks, as no matter how good you build it wood will flex and wood also will compress at different rates due to grain structure and knots, so in fact you can have a perfect wood frame compress at different rates causing unevenness and tank cracking.

Steve

[Aquattro]

Oh, no!:(



so far my story is that it's a leaking bulkhead, accumulating water in the bottom trim. It's dripping back into the sump, so that's a good thing. Right? :)

[Reefer Rob]

The foam on all tanks should only be max 4" wide around the perimeter of the tank, allowing the center of the bottom glass to float.

[The Grizz]

So what if you have a tank that has the trim and you have holes drilled down the center of the tank for returns?

Not sure if the tank has a floating bottom yet but with all the rock that is going to go in it and sand how do you support the glass so it does not break from where the holes are?

[Borderjumper]

so far my story is that it's a leaking bulkhead, accumulating water in the bottom trim. It's dripping back into the sump, so that's a good thing. Right? :)

I read your first post and just went OMG! It's contagious ! I'm glad it's "just" a bulkhead. Sounds like if it's leaking into the sump you haven't lost any water, so that's a good thing.

[Borderjumper]

I've googled all morning, and what I am finding is.. Never put foam under a rimmed tank. A rimmed tank is designed so that the weight of the tank sits on the rim, which displaces the weight up the sides vertically. makes sense, as glass it strong vertically and weak horizontally. IF you put a rimmed tank on styrofoam, the weight bearing edge will compress into the foam until the glass is being pushed down onto the foam, your now messing with the design intent and instead of all the force of the weight being transferred vertically up the sides, it's also pressing up on the glass bottom which eventually cause it to flex, and as I know only too well, horizontal glass doesn't flex well when the corners are being pinned down by over a 1000lbs of water and rock.

[MitchM]

so far my story is that it's a leaking bulkhead, accumulating water in the bottom trim. It's dripping back into the sump, so that's a good thing. Right? :)

Um no, Brad, any leak is a bad thing - otherwise Borderjumper would be overjoyed right now...:razz:

I don't get how the styrofoam under the tank would be a bad thing. If the glass is supported, then it's supported and should be stronger.
I can see if the supporting structure is uneven or warped, then you would have a problem.

Mitch

[Borderjumper]

Um no, Brad, any leak is a bad thing - otherwise Borderjumper would be overjoyed right now...:razz:

I don't get how the styrofoam under the tank would be a bad thing. If the glass is supported, then it's supported and should be stronger.
I can see if the supporting structure is uneven or warped, then you would have a problem.

Mitch

I think it's a very fine line between the bottom glass being supported, and the bottom glass being pushed up by the foam as the edges compress down.

[MitchM]

It shouldn't be that fine of a line. I've had 6' pieces of glass bow out 1/4" with no ill effects. Pink foam doesn't compress that much, does it?
A couple thousand pounds of water and rock pressure on the bottom glass should balance out the downward pressure from the edges. That would result in less pressure on the edges.
(just trying to wrap my head around the physics of the foam problem)

Mitch

[Doug]

Shelley, although not much help now, sorry, but I agree with no foam under a framed tank. We had many threads on RC in regards to it. One builder even said it voids there warranty if foam is used under a frame.

Any tank thats custom made, with no frame, where the complete bottom sits on the foam is usually fine.

[Borderjumper]

It shouldn't be that fine of a line. I've had 6' pieces of glass bow out 1/4" with no ill effects. Pink foam doesn't compress that much, does it?
A couple thousand pounds of water and rock pressure on the bottom glass should balance out the downward pressure from the edges. That would result in less pressure on the edges.
(just trying to wrap my head around the physics of the foam problem)

Mitch

If you look at the picture I posted above, the foam WAS compressed visibly along the edges. My theory is it compressed as much as it could until it made the bottom so tight it popped.

We just popped a piece of the trim off, and this tank is bottom glass with the sides all on top of the bottom glass.

[Borderjumper]

Shelley, although not much help now, sorry, but I agree with no foam under a framed tank. We had many threads on RC in regards to it. One builder even said it voids there warranty if foam is used under a frame.

Any tank thats custom made, with no frame, where the complete bottom sits on the foam is usually fine.

Thanks Doug.. I'm just trying to come to a conclusion as to why this tank failed.. I'm prolly going to have a new one built and I don't want this happening again.

I think there is some confusion as to what foam I used. It's not spongy carpet underlay type foam. I have other tanks sitting on very thin open cell black actual foam.. Spongy foam.. I think that's ok as it can totally compress.
This pink building insulation sheet foam is over 1/2 thick and will not hardly compress even if you stand on it. IMO it's so rigid that once the tank edge settles IN to the foam the whole middle of the tank has an upward force pushing against it.

I won't use it again,, I'm going back to the thin open cell spongy foam, if any foam at all.

[Madreefer]

IMO it's so rigid that once the tank edge settles IN to the foam the whole middle of the tank has an upward force pushing against it.

Makes perfect sense to me. I agree. If tanks were designed to have any foam under the tank than why do they not come that way? Or why do they not sell the correct sized precut peices? Good money maker especially for odd shaped tanks? Someone posted about glass bowing out. Maybe there is supposed to a little bit of bowing out underneath.

[MitchM]

At any rate, sorry to hear about your tank break.
Not a nice thing to have happen at any time of the year.

Mitch

[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 :razz:

[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

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.

http://i6.photobucket.com/albums/y240/Carrida/IMG_0659.jpg

[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/foam/products/foamular-250.aspx




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]

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