# Tank not sitting flush in middle



## islanddave1 (Jul 5, 2013)

Hello All

I finally got my stand built and it is well made and straight. 3/"4 plywood top and 2x6 inner construction.

I placed the tank on the stand, and although all four corners of the tank touch the top of the stand the bottom trim of the tank both front and back do not. This starts at the middle and goes to about 6" from each corner. The side do not do this. 

250 gallons 60"L x 36"W x 27"H

Should I be concerned?
Hard to capture in a picture removed wiers going with a hob life reef and using an old ehiem for a closed loop

FYI .085" clearance max at middle 

Thanks David


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## PlantedRich (Jul 21, 2010)

This is kind of a frequent question in different forms and it always gets mixed opinions. My personal opinion is that it is not a problem. 
My reasons go like this. One is that I used to have a job where I worked in people homes a lot and much of the time, I worked a college area. I often saw tanks set up on temporary stands may of columns of concrete blocks supporting only the ends of tanks. College means moving and blocks can be hauled real easy in cars so it makes good college stands. But that is the extreme end of what you have. The middle along the sides is not supported at all but it works fine. 
I think of the tank much as a railroad bridge making a "C" channel. If you are familiar with C channel it is extremely hard to bend. Next step up is the "I" beam! As long as the sides can't bow outward, the sides will certainly not bow downward. And we assume that the sides and bottom are connected well as they have to resist the weight of the water pushing out. 
I see it work and I know it is okay but still there is this part of us that says "DANGER! If it bothers you, it requires a fix of some sort. But to make myself feel better, I would look at some footpaths or bridges to see how they are made to support the weight when only the ends are on columns. Railroad bridges? 
Good luck but I think it is fine.


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## Nordic (Nov 11, 2003)

I's slap some extra thick polystyrene foam (2") under it... That should eat up any of the slack.


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## kevmo911 (Sep 24, 2010)

I don't have any personal experience with tanks having issues with not being supported in the middle. I have, however, spent a lot of time reading through threads about DIY stands, and, for the most part, 4 feet is the longest people recommend having a stand without at least one center support (not all, but most). And, even at 4 feet, many designs have a center support. So, based on what I've read, I wouldn't build a stand for myself that was over 4 feet that did not have a center support.

And yes, I'd be at least as concerned as you are that I could see light under the center of the tank.


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## touch of sky (Nov 1, 2011)

I second the suggestion of the polystyrene.


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## mistergreen (Dec 9, 2006)

+1 on foam sheet.


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## Hilde (May 19, 2008)

Obvious the wood was not straight to begin with. Thus the front piece may not be strong enough to hold all of the water. Thus I think you should brace the middle more. 

+2 on foam sheet too.


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## shrimpNewbie (May 6, 2011)

kevmo911 said:


> I don't have any personal experience with tanks having issues with not being supported in the middle. I have, however, spent a lot of time reading through threads about DIY stands, and, for the most part, 4 feet is the longest people recommend having a stand without at least one center support (not all, but most). And, even at 4 feet, many designs have a center support. So, based on what I've read, I wouldn't build a stand for myself that was over 4 feet that did not have a center support.
> 
> And yes, I'd be at least as concerned as you are that I could see light under the center of the tank.


The center support beams are really only needed for rimless and acrylic tanks. The tank on this stand will be perfectly fine. 

Sent from my SM-N910T using Tapatalk


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## shrimpNewbie (May 6, 2011)

Just take a gander at cinder block stands I've seen over 400 gallons supported only on the edge. If you really want the peace of mind throw a high density foam mat under it, yoga mat material is great but not thick enough. Styrene is not my favorite as it doesn't really offer any resistance

Sent from my SM-N910T using Tapatalk


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## islanddave1 (Jul 5, 2013)

PlantedRich said:


> This is kind of a frequent question in different forms and it always gets mixed opinions. My personal opinion is that it is not a problem.
> My reasons go like this. One is that I used to have a job where I worked in people homes a lot and much of the time, I worked a college area. I often saw tanks set up on temporary stands may of columns of concrete blocks supporting only the ends of tanks. College means moving and blocks can be hauled real easy in cars so it makes good college stands. But that is the extreme end of what you have. The middle along the sides is not supported at all but it works fine.
> I think of the tank much as a railroad bridge making a "C" channel. If you are familiar with C channel it is extremely hard to bend. Next step up is the "I" beam! As long as the sides can't bow outward, the sides will certainly not bow downward. And we assume that the sides and bottom are connected well as they have to resist the weight of the water pushing out.
> I see it work and I know it is okay but still there is this part of us that says "DANGER! If it bothers you, it requires a fix of some sort. But to make myself feel better, I would look at some footpaths or bridges to see how they are made to support the weight when only the ends are on columns. Railroad bridges?
> Good luck but I think it is fine.


Thanks for your advice it seems to make good sense. Actually I remember the bridge analogy from a long time ago when I was researching the building of the stand. For piece of mind I think I will place some foam under the tank, but just under the perimeter of the rim. One because that's only where it is needed and two because it will be easier. What size foam would you recommend. I really don't think it really has to be too thick. I'm thinking 1/4" should be more than enough. Do you think a yoga would suffice?


Thanks for your help


David


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## islanddave1 (Jul 5, 2013)

shrimpNewbie said:


> Just take a gander at cinder block stands I've seen over 400 gallons supported only on the edge. If you really want the peace of mind throw a high density foam mat under it, yoga mat material is great but not thick enough. Styrene is not my favorite as it doesn't really offer any resistance
> 
> Sent from my SM-N910T using Tapatalk


What is your opinion on these?


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## GraphicGr8s (Apr 4, 2011)

If the tank is on a full sheet of foam it is possible that the rim could compress the foam under it and force the entire bottom glass to be on that foam. There are stories, however anecdotal, that caused the bottom glass to crack if the foam was to be trapped between the stand and the glass.

If it bothers you either shim the tank right in the middle. No need to go the entire area that's shy. And then put a trim to hide it all. If you only nailed the plywood to the frame you can shim under the plywood and hide the gap entirely.


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## PlantedRich (Jul 21, 2010)

I would not bother with either but then the yoga mat will likely do what is wanted. The ends will compress more than the center and all will look supported. But that is where my thoughts get back to what amount are we really doing if we place a heavy item on something we can compress with our fingers? I f we want to support the center to keep it from bowing in some way, will something that squishy really support much or will the tank that wants to bow down jus go ahead and squish the squishy stuff?
I see it going this way IF the tank center is going to bow down. When we put the weight on it, the tank ends will squish down from the starting height of whatever thickness we use. Say we use 1/2" and the ends sink 1/4", leaving the center somewhere above that but willing to bow down. What keeps the center from bowing down? We've already said the ends will compress the foam so is there reason to believe the center can't do the same if it will bow down? 

I just see the foam as a place where water that gets spilled can collect between the foam and wood. That is a spot that I can't reach to wipe up so it can set there and eventually become mold, mildew, or rot that I don't need. 

For the need of support at the centers of long tanks, I do add a support but not for the tank bowing. I find a 6' long 2X will have a fair amount of moisture left even if it is kiln dried. That means that if I get the wrong one and lay it the wrong way, it may twist from end to end as it dries. The twist can ruin the level top surface so an easy way to prevent that twist even if I choose poorly and build poorly is to add a vertical 2X4 under the horizontal, at or near the middle. For my design stands, the vertical 2X also makes a good solid framework for the door or doors. 
Some designs use a horizontal 2X for the 6" length to stop the twist but that is more weight and expense for the longer lumber and is not useful for door framing. Different designs for different ideas?


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## shrimpNewbie (May 6, 2011)

islanddave1 said:


> Thanks for your advice it seems to make good sense. Actually I remember the bridge analogy from a long time ago when I was researching the building of the stand. For piece of mind I think I will place some foam under the tank, but just under the perimeter of the rim. One because that's only where it is needed and two because it will be easier. What size foam would you recommend. I really don't think it really has to be too thick. I'm thinking 1/4" should be more than enough. Do you think a yoga would suffice?
> 
> 
> Thanks for your help
> ...


I would say go with a half inch thick mat if at all. Another person recommended shimming the center under the ply, that would probably be my move you can easy shim the whole way add wood filler in between the support and ply and you're good. 

Sent from my SM-N910T using Tapatalk


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## jr125 (Mar 5, 2015)

GraphicGr8s said:


> If the tank is on a full sheet of foam it is possible that the rim could compress the foam under it and force the entire bottom glass to be on that foam. There are stories, however anecdotal, that caused the bottom glass to crack if the foam was to be trapped between the stand and the glass.
> 
> If it bothers you either shim the tank right in the middle. No need to go the entire area that's shy. And then put a trim to hide it all. If you only nailed the plywood to the frame you can shim under the plywood and hide the gap entirely.


Both of these comments make sense to me. The tank is designed to be supported at the frame, not the glass. The small footprint of the frame on the foam would cause it to compress much more than the foam under the glass. With the large surface area of the glass the foam it contacts could cause it to push away from the frame. The shim at the frame makes more sense as long as the material under it provides adequate support. 

I get the C channel concept but have a little trouble with it when it comes to aquariums. With an aquarium the load is between the sides of the tank and the support provided by the sides is only as good as the joint connecting the sides to the bottom. If you flip the C channel over the sides(vertical) and top(horizontal) all have the load on top of them. The only purpose of a joint is to provide stability to the structure if needed at all.

I've read so many comments with regard to tanks small and large having been successfully supported at the ends only that it is impossible for me to not accept the fact that end support is all that is necessary. I do believe that there is benefit to adding center support though, especially with very large tanks. It is just a matter of what makes you more comfortable I guess.


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## Nexgen (Jul 1, 2015)

From someone who has done some construction work before and I'm in school to becoming an engineer, I would add a center support. Look at it this way, when they design a tank they factor in a safety factor when choosing the glass thickness, this is usually a factor of 3.8. That means that the glass is 3.8 times thicker than it absolutely has to be. Wouldn't you want to have a similar safety factor for the stand. A 2x6 can support about 7,000lbs at a length of 9' if supported every 16", so at a length of 5' I would estimate that a 2x6 can support 10,000lbs. With a saftey factor of say 4 you would be able to support a weight of 2,500lbs if supported every 16", which you aren't. But the weight is distributed over two beams which could intern support 5,000lbs if supported every 16". So if you support the beams every 32", in your case 30", then I would say you could support around 2,500lbs. Which just so happens to be about the weight of your tank when filled.
If you support the center portion of the glass you will be taking pressure away from the corners, and distributing the weight more evenly. The more evenly the tank is supported the longer the tank will last and the less likely you are to end up with 250 gallons of water on your floor.
If it were me I would put a jack in between the bottom and top beams and apply enough pressure to straighten the top beam, then I would cut the support to fit snugly into the center. This would force the beam straight. Over time wood shrinks and swells, which means that the beam could bow even more without a center support, when it does so, it may apply more pressure to the outer posts and pull them in. The opposite could also happen; the weight of the tank resting on the high points of the beams may straighten them out. Either could happen, but personally I wouldn't risk it.
The tank doesn't look filled and to add a support you don't need to move the tank. So why not take like 10 min to add a extra support. If the thought crosses your mind that there could be a problem, then there probably could be a issue. Adding the support will give you piece of mind that everything is going to be fine in the long run.


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## jr125 (Mar 5, 2015)

Nexgen said:


> From someone who has done some construction work before and I'm in school to becoming an engineer, I would add a center support. Look at it this way, when they design a tank they factor in a safety factor when choosing the glass thickness, this is usually a factor of 3.8. That means that the glass is 3.8 times thicker than it absolutely has to be. Wouldn't you want to have a similar safety factor for the stand. A 2x6 can support about 7,000lbs at a length of 9' if supported every 16", so at a length of 5' I would estimate that a 2x6 can support 10,000lbs. With a saftey factor of say 4 you would be able to support a weight of 2,500lbs if supported every 16", which you aren't. But the weight is distributed over two beams which could intern support 5,000lbs if supported every 16". So if you support the beams every 32", in your case 30", then I would say you could support around 2,500lbs. Which just so happens to be about the weight of your tank when filled.
> If you support the center portion of the glass you will be taking pressure away from the corners, and distributing the weight more evenly. The more evenly the tank is supported the longer the tank will last and the less likely you are to end up with 250 gallons of water on your floor.
> If it were me I would put a jack in between the bottom and top beams and apply enough pressure to straighten the top beam, then I would cut the support to fit snugly into the center. This would force the beam straight. Over time wood shrinks and swells, which means that the beam could bow even more without a center support, when it does so, it may apply more pressure to the outer posts and pull them in. The opposite could also happen; the weight of the tank resting on the high points of the beams may straighten them out. Either could happen, but personally I wouldn't risk it.
> The tank doesn't look filled and to add a support you don't need to move the tank. So why not take like 10 min to add a extra support. If the thought crosses your mind that there could be a problem, then there probably could be a issue. Adding the support will give you piece of mind that everything is going to be fine in the long run.


I made almost this exact argument for additional center support previously and I'm not sure I got anywhere with it. Even if it is not needed it will reduce the load stress and the risk of failure.


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## Nexgen (Jul 1, 2015)

jr125 said:


> I made almost this exact argument for additional center support previously and I'm not sure I got anywhere with it. Even if it is not needed it will reduce the load stress and the risk of failure.


I'm going to be honest I read the first few replies and saw where this was going so I just added my side. If anything I thought I would at least reiterate what someone else said.


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## Mikevwall (Jul 27, 2015)

Cork Sheet > Foam sheet.


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## islanddave1 (Jul 5, 2013)

I'm not sure that attempting to straighten the top beam will produce positive effect. I am investigating shimming between the plywood and top beam. I have also cut a middle support for the front, inspite of contrary information from the source in which aided my design of the stand. Reason being.....fear. plain and simple. The stand is now overbuilt in every respect. I have placed a call to the vendor to ask for manufacturer advice. I have contacted others who have this same tank with diy stands and they have had similar issues. Interesting fact is that this phenomenon of the tank not touching in the center seems to be more common that I would think. Interestingly a commercial stand almost always has a trim that would obscure this revelation if it occurred and one would be none the wiser. Of course maybe a commercial stand would be more.straight too? I'm sure the manufacturer will recommend one of their stands.....which h will.retain the tanks warranty. I might just give up the ghost and buy the commercial stand. Though after reading much about this I'm incline to think that foam under a rimmed tank might just be a placebo effect for the owner.


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