Too Much Polystyrene?

[malfunction]

Hi all,

I'm in the process of finishing the repairs to my 8x2x2 tank, and will probably be water testing it next weekend. As an uneven surface caused it to crack last time, I'm being super cautious this time around. I currently have it sitting on 25mm thick polystyrene, but am considering using twice as much (i.e. 50mm) when I set it up. Are there any risks to having to much polystyrene under the tank? Or can you never have too much?

Thanks

 

[Alasse]

Wont hurt having a good thickness underneath

 

[DerpPH]

Yeah good distribution of weight does make it more stable

 

[Brilly91]

I had a tank on 50mm, i dont know if it made a huge difference but it didnt create any issues

 

[ShinySideUp]

Some tanks come with a frame on the bottom and they expicitly forbid the use of polystyrene; my six footer is one of these. The framework holds the glass off the supporting surface and it supports the tank around the edges, something which I find counter-intuitive as it means the whole weight of tank and decorations rests on a largely unsupported glass panel. My tank manufacturer says in their instructions that if the frame is not used the tank must be rested on 5mm polystyrene; they don't give an upper limit.
 
The OP says he is using a 25mm polystyrene base, this seems to be incredibly thick, almost an inch! I think that might be rather too much as the idea of a PS base is to prevent small particles causing strain points and you wouldn't need a huge thickness to do this. Indeed, the greater the thickness of PS the more likely that there would be weak points in places which would allow the tank to sink further in some places and not in others thereby causing more strain.
 
5mm seems a reasonable thickness.

 

[Alasse]

I'm off to see my tank builder (he makes them commercially for his fulltime job) this week actually, i will ask him
 
 
I truely believe, and cannot see how, having extra thick foam under your tank will cause any problems, but as i said above i will ask the professional and get back to you

 

[Ch4rlie]

I, for one, agree with ShinySideUp statement.

Floating tank base is one that supports the entire tank on a plastic or sometimes wooden base that has no need for polystyrene.

Rimless tanks which has no bottom plastic or wooden base tend to need a polystyrene base, usually about 5 - 10 mm. These polystyrene is basically to help level the tank a little but but main purpose is to support entire bottom from uneven surfaces.

For example, any tiny bits of dirt or stone debris that's been missed and the tank rests on top of this will create a pressure point, more often than not, will crack the bottom if the glass. The same for any uneven surfaces. The polystyrene proctects this from occurring. That's its main job.

Having any polystyrene thicker than say 15mm, at a guess, basically defeats this purpose, any extra weight in the tank, rocks or decor on one side of tank, will unbalance the tank and that side will probably sink into the polystyrene unevenly. Therefore making an unlevel tank and creates pressure points at the joins and side glass.

I have heard of horror stories of folks who have done similar things, but on other hand, a few others have reported no problems.

Personally, I would not take the risk with any non floating based tanks with thicker than necessary polystyrene.

 

[malfunction]

Ok, thanks for the info everyone. As with many things in fishkeeping, it seems there are contradictory perspectives on this.

@Alasse: I'd be grateful for the feedback from you tank builder.

@Brilly: how big was you tank? And how long did you keep it for?

@ShinySideUp & Ch4lie: just want to check I correctly understand your perspective...are you saying that the biggest risk is that it will amplify any weight differences caused by the decorations inside the tank? If so, does this mean that, providing I distribute the decorations evenly across the tank floor, I needn't work about this because the tank will sink evenly into the polystyrene?

 

[ShinySideUp]

@ShinySideUp & Ch4lie: just want to check I correctly understand your perspective...are you saying that the biggest risk is that it will amplify any weight differences caused by the decorations inside the tank? If so, does this mean that, providing I distribute the decorations evenly across the tank floor, I needn't work about this because the tank will sink evenly into the polystyrene?

 
A greater thickness of PS will give more where there is greater weight, that's why a thinner layer is better as the difference between uncompressed and totally compressed is then very small. So long as the PS is thick enough to protect against small particles pressing on the tank it should be as thin as possible so you would be able to put your decorations wherever you want.
 
I might also point out that any rocks you use will probably not rest on the glass bottom and as such their weight will not significantly affect the glass base at all since the weight of the rocks is far exceeeded by the weight of the water.

 

[Alasse]

Ok...spoke to my tank builder this morning. He said as long as the foam is the correct density it wont make any difference.

Nor will having a heap of rocks one end and not the other, on thick foam make a difference...
 
Take that as you will

 

 

[Ch4rlie]

What is the correct density?

Is there a way to tell the difference?

Did your source say if the density is too soft, what would happen with the tank?

Really intriguing and would love to know more

 

[Alasse]

I dont know, i just buy the foam thats under my tanks off him, & I'm sure there is a way to tell the difference, i didnt ask him lol
 
If the foam is not dense enough, regardless of thickness, the tank could crack, that i did ask him lol
 
He did also say, tanks tend to crack from the stand (design/not level/etc) rather than anything to do with the foam