How Bad is this?

[firecrackerbob]

setting up a tank I got for free last weekend(55). In doing so I noticed that the center of the tank has a gap between the stand and the tank. Never noticed this before on past tanks on this stand so I am inclined to think its the tank(very old tank). heres a pic:
http://www.wikisift.com/WikiPics/gap.jpg

my plan was to add some shims to support it, but I thought I would put it to the group on thoughts on how hazardous this is? I would estimate it to be about a 1/4in bow in the center of the 48in long tank. this is an old style tank so the pane thickness is almost 1/2in and not tempered.
what do you guys think?
Thanks
E

 

[a1amap]

When I filled the 75 I had a small gap and used shims and silicon.

 

[kaptken]

Was that pic with the tank full? The water load will sag the bottom plate down a bit when full, but not the side plates. When i set my 75 up 9 years ago? I saw a gap in places too, because of the floor , stand, or who knows what. So I put down a recommended strip of 1/8 inch styrofoam sill plate insulation BETWEEN the tank and stand. It helps spread the load.

When full the tank frame, which is what you are looking at, will sag down, and the foam will compress where needed and help distribute the load evenly.

Not sure, but the tanks may be made slightly concave down to take the water load. Although, glass does not behave like steel or concrete. If you figure the total weight of water, sand and rock in a 55, about 500 pounds, distributed around the base perimeter, 2x48 + 2x13 = 122 inches, It comes to about 4 pounds per linear inch of base support. I think the foam can compress enough as required and transfer most of that load.

I have seen old LFS that only had their tanks supported by the two end plates. no support along the front or back long sides. at least the 30 longs and 40 breeders. maybe 55s. ?

Anyway, do a little foam shimming and it should hunker down just right. the foam is a better choice than a point shim. The foam will spread the Load out. The shim will concentrate the load at the point of the shim. HMMM? That not good...

Go Foam.

 

[firecrackerbob]

Thanks Guys!
That pic was with the tank empty, but I observed at least a 1/8in gap even full. I added the layer of foam, moved the tank to a more stable spot in the house and put a brace against the wall to make sure there is no wobbling... so far so good!
I am going to refill the tank this evening to see how it all turned out, but I think its good to go and I feel much less paranoid now with the mods.
thanks again
E