Polystyrene between tank and stand

[Spaced Cowboy]

Hi all,

So, from what I've read, it appears to be canon that if a tank has a plastic rim, putting an expanded-polystyrene sheet between the stand and the tank is a no-no. The tank-manufacturer (glasscages) I got my tank (which has a plastic rim around the base) from, though, states "A sheet of 3/4" Styrofoam (reaching completely side-to-side and front-to-back) must be placed between the tank and the surface of the stand." (see the "warranty" (http://www.glasscages.com/?sAction=AqWarranty))

So, I got to thinking about it. The tank is 8' x 2' x 2' (a standard 240 gallon tank), and the polystyrene they supplied was ~0.5" thick. According to the calculator (http://boonedocks.net/fishtank/ftweb.php), I'll have ~3000 lbs to support on that rim.

The rim is ~1" wide, so we have approximately (96+96+24+24) square inches to support 3000 lbs, which leads to a load of ~12.5 psi. There is a table showing how expanded polystyrene deforms with load at http://www.universalconstructionfoam.com/resources/geofoam-data-sheet.php. If we take the worst-density foam (let's assume glasscages aren't supplying super-quality packaging!), then at 12.5 psi, it is quickly going to deform to where the entire base of the aquarium is supported.

So, the equation now changes, and you have (96x24) square inches supporting 3000 lbs, for a load of 1.3 psi.

Now, 1.3 psi on even the worst-density foam won't deform that foam by even 1% of its thickness. At this point, the support offered by the foam would appear to be complimentary to the entire underside of the aquarium base.

So, what's the problem with foam between the tank and the stand ? I should mention that GC seem to make their tanks (well, mine is this way, anyway) with the sides sitting on top of the base, *not* with a "floating" base between the side walls. Even with a floating base, I think the minimal deformation would make it well-supported, but with a non-floating base I really can't see why there would be a problem.

So, back to the start. Considered wisdom is that foam is a bad idea. What am I missing ?

Simon

[barjam]

I believe glass cages is the only manufacturer of tanks with plastic bottoms that suggest using the foam. I seem to remember that it actually voids the warranty of other plastic rim tank manufacturers. Considering how poorly constructed glasscages tanks seem to be (all the complaints on the forum) perhaps they don't know what they are talking about. Who knows.

Supporting the tank by the bottom glass would be a very bad idea I would think as they aren't designed for that. Now if you had very rigid foam on a very level surface I would think that would be ok but if you had a level surface to begin with the foam would be pointless in the first place.

[Spaced Cowboy]

I believe glass cages is the only manufacturer of tanks with plastic bottoms that suggest using the foam. I seem to remember that it actually voids the warranty of other plastic rim tank manufacturers. Considering how poorly constructed glasscages tanks seem to be (all the complaints on the forum) perhaps they don't know what they are talking about. Who knows.

Actually, I think it's just a crap-shoot what sort of tank you get from GC. I'm happy with mine (so far :) ): the seams are nicely done, it's built like a tank (pun intended) and frankly it looks very nice. They claim to make ~100 tanks per week, and perhaps their QA isn't up to scratch, but in all the forums you see of people complaining, there are also people saying they're very happy with their tank.

Another point is that a lot of people seem to be turned off by their customer-service. Again, the lady on the end of the phone couldn't have been nicer. I guess I have no complaints there either.

I didn't really mean to make this into a GC thread though, so...


Supporting the tank by the bottom glass would be a very bad idea I would think as they aren't designed for that. Now if you had very rigid foam on a very level surface I would think that would be ok but if you had a level surface to begin with the foam would be pointless in the first place.

This is what I want to know. Why is supporting the tank along the bottom a bad idea ? How can it hurt matters if something is supported ? I can see how it could hurt if it wasn't supported, but I can't see why having a supported section of tank is a bad thing. The very worst I'd have thought it could be was zero-gain, and frankly that seems unlikely.

Simon.


This is assuming you don't have a floating base. As I mentioned in the original post, I could see it *possibly* being an issue for a floating base if there is differing support for the sides and walls, somehow.

[Gorgok]

They claim to make ~100 tanks per week, and perhaps their QA isn't up to scratch, but in all the forums you see of people complaining, there are also people saying they're very happy with their tank.

Another thing to note related to this, most people will complain about defects while only some will praise for a job well done. I know i have never praised my tank (not a GC tank nor is it glass) simply because its doing what it should, the end.

As for the real question, is tempered glass only strong one way? If that were the case i would see supporting the bottom as very bad indeed.

[merfish101]

Just curious, any more thoughts on this subject?

[djbon]

I will never put a tank (glass tank) without polystyrene sheet between the tank and the stand even if the stand is perfectly leveled. You can come up with all the scientific formulas and calculation, it only need a fraction of pressure point deviation at any single spot to crack the bottom glass and flood your house. Thank you.

[ca1ore]

Just curious, any more thoughts on this subject?

Yeah, I think one should follow the recommendation of the tank manufacturer rather than the opinions of RC members; the vast majority of whom know not of what they speak (at least on this topic). The irony is that tank manufacturers also recommend using their stands - which a decent percentage (including yours truly) don't follow.

[davocean]

^^ Exactly what he said

[djbon]

After reading the post #1 for the second time, yes for a tank with a plastic rim bottom or floating base tank, just follow the manufacturer recommendations. Personally for a tank with all side panels are sitting on top of the bottom glass panel, polystyrene padding will reduce the chances of cracking when filled.

[NanoReefWanabe]

Supporting the tank by the bottom glass would be a very bad idea I would think as they aren't designed for that. Now if you had very rigid foam on a very level surface I would think that would be ok but if you had a level surface to begin with the foam would be pointless in the first place.

The purpose of the foam is not to fix unlevelness, foam is strictly meant to relieve pressure points created by dirt dust hair etc.

to the OP,
you are supposed to use high density poly styrene like celfort300. A product designed to be used below grade and support weight....by the sound of it you are basing you calculations on packaging foam (white pebbly stuff) and that should not be used...my appologies if this is what they sent you to use then so be it....if they sent you the pink or blue or purple rigid then again my bad .

Do you have a pic of the bottom rim if your tank? I have never seen a tank built on the bottom and incorporate a plastric trim.

On a side note something else to remeber is GC will warrant the tank if you follow thier directions, sadly they wont cover the 40k worth of damage 240g of water will do.

[djbon]

I never come across a rimmed trim bottom myself. Almost all glass tank being built in my place are those with all side panels sitting on top of bottom glass panel.