Tank not sitting flush in middle - The Planted Tank Forum
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post #1 of 20 (permalink) Old 01-23-2016, 11:30 PM Thread Starter
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Tank not sitting flush in middle

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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post #2 of 20 (permalink) Old 01-24-2016, 03:26 AM
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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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post #3 of 20 (permalink) Old 01-24-2016, 03:38 AM
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I's slap some extra thick polystyrene foam (2") under it... That should eat up any of the slack.

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post #4 of 20 (permalink) Old 01-24-2016, 07:48 AM
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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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post #5 of 20 (permalink) Old 01-24-2016, 02:32 PM
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I second the suggestion of the polystyrene.
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post #6 of 20 (permalink) Old 01-24-2016, 02:42 PM
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+1 on foam sheet.


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post #7 of 20 (permalink) Old 01-24-2016, 02:54 PM
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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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post #8 of 20 (permalink) Old 01-24-2016, 03:19 PM
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Quote:
Originally Posted by kevmo911 View Post
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.

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post #9 of 20 (permalink) Old 01-24-2016, 03:22 PM
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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

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post #10 of 20 (permalink) Old 01-24-2016, 09:46 PM Thread Starter
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Quote:
Originally Posted by PlantedRich View Post
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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post #11 of 20 (permalink) Old 01-24-2016, 11:57 PM Thread Starter
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Quote:
Originally Posted by shrimpNewbie View Post
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

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What is your opinion on these?

http://www.amazon.com/We-Sell-Mats-Interlocking-Anti-Fatigue/dp/B001EJPGG4%3Fpsc%3D1%26SubscriptionId%3DAKIAILSHYYTFIVPWUY6Q%26tag%3Dduckduckgo-d-20%26linkCode%3Dxm2%26camp%3D2025%26creative%3D165953%26creativeASIN%3DB001EJPGG4
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post #12 of 20 (permalink) Old 01-25-2016, 12:26 AM
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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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post #13 of 20 (permalink) Old 01-25-2016, 01:53 AM
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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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post #14 of 20 (permalink) Old 01-25-2016, 12:40 PM
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Quote:
Originally Posted by islanddave1 View Post
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
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.

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post #15 of 20 (permalink) Old 01-25-2016, 01:48 PM
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Quote:
Originally Posted by GraphicGr8s View Post
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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