What size lumber to hold up a 55g from its corners? - The Planted Tank Forum
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post #1 of 12 (permalink) Old 10-15-2017, 11:59 PM Thread Starter
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What size lumber to hold up a 55g from its corners?

I would like to build a two level stand with a 55g on top.

Because there will be a tank on the bottom, there can't be any middle supports, it will need to be supported from corners. There are some metal stands designed this way.

There will be two cross beams supporting the tank, and a 3/4" piece of MDF for the top that will be affixed to the beams and will add additional support. The rear of the top will likely also be supported from below.

Will two 2x4s be strong enough to avoid sagging, or should I use 2x6? Or possibly three beams of 2x4?
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post #2 of 12 (permalink) Old 10-16-2017, 04:19 AM
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Might want to go through this a bit:
https://www.monsterfishkeepers.com/f...old-up.302232/
http://www.awc.org/codes-standards/c...tware/spancalc

2x4's should work.
Def if using better grade/species of wood.
Personally would do 2x6's..just because.

Your design will be more important than wood type/size

A 55gal weighs approx 550lbs filled..

Bigger question is why MDF for the top? Susceptible to water damage.
MDF is basically glorified cardboard..
Cabinet grade plywood would be much better..

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Like Big G mentioned MDF will disintegrate when water is present.
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Last edited by jeffkrol; 10-16-2017 at 04:28 AM. Reason: edit
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post #3 of 12 (permalink) Old 10-16-2017, 01:43 PM Thread Starter
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Originally Posted by jeffkrol View Post
Might want to go through this a bit:
https://www.monsterfishkeepers.com/f...old-up.302232/
Maximum Span Calculator for Wood Joists and Rafters

2x4's should work.
Def if using better grade/species of wood.
Personally would do 2x6's..just because.

Your design will be more important than wood type/size

A 55gal weighs approx 550lbs filled..

Bigger question is why MDF for the top? Susceptible to water damage.
MDF is basically glorified cardboard..
Cabinet grade plywood would be much better..
I have an old desk that I will disassemble and use for the exterior shell, the shelves, and the door. There are many MDF parts that can be repurposed, and it will save me from having to refinish all of it. Underlying frame will be solid wood, but the visible surfaces will be mdf.
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post #4 of 12 (permalink) Old 10-16-2017, 04:38 PM
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Exterior "shell" if non-supportive is fine..
It's the top I question..

To be honest, "I" woudn't use it.. YMMV..

Laminate is a fairly good seal though..

When I worked for a cabinet maker we did use MDF for some desktops but min thickness was 1 1/4" (or close, long time ago)
MDF was never a choice for quality work..Don't remember even our melamine boards were MDF core.
as I said.. a long time ago.

Works well for speaker cabinets though..Lack of grain and density is a plus..


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post #5 of 12 (permalink) Old 10-16-2017, 05:03 PM
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There's a build thread on here where a someone who does this kind of stuff for a living calculated how much the 2x4 stand of one of the common designs(the one I followed for my rack) would hold, it was a huge number. That build was for a 100+ gallon tank, a 55 will definitely be fine with 2x4s. I used 3/4" ply for my top & bottom shelves. I'll try to find that thread.


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post #6 of 12 (permalink) Old 10-16-2017, 05:31 PM Thread Starter
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Originally Posted by johnson18 View Post
There's a build thread on here where a someone who does this kind of stuff for a living calculated how much the 2x4 stand of one of the common designs(the one I followed for my rack) would hold, it was a huge number. That build was for a 100+ gallon tank, a 55 will definitely be fine with 2x4s. I used 3/4" ply for my top & bottom shelves. I'll try to find that thread.


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Thanks. A few months ago I bought a commercial stand, and I figured with a 2x4 frame and using the prefinished MDF for exterior surfaces, it will look quite good. I have been meaning to take this desk to the landfill, so I might as well reuse it.

Jeff, the desktop is 1" MDF. The tank would be fully supported by the frame, this would just be for cosmetics.

Bump: In this stand design, why does the inner green beam not go to the top of the frame?

https://www.monsterfishkeepers.com/f...te-jpg.455260/
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post #7 of 12 (permalink) Old 10-16-2017, 06:00 PM
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Just support for assembly/lineup mostly..but also ease of assembly of "purple" legs. That is discussed in the thread..

anyways more fun and how to use just plywood..
Most people don't have a pocket joiner though and didn't mention glue.. Lots of glue..

As structurally sound as it is .. still makes me shivver...
not so much for compression strength.. but racking

https://www.reef2reef.com/threads/st...d-sump.289749/
{SEE big white plywood stand for 200g plus tank post #18}

One last thing for most builders.. Screwing into end grain is problematic at best..

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Last edited by jeffkrol; 10-16-2017 at 06:15 PM. Reason: edit
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post #8 of 12 (permalink) Old 10-16-2017, 06:16 PM Thread Starter
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One last thing for most builders.. Screwing into end grain is problematic at best..

Yeah, even I know that...
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post #9 of 12 (permalink) Old 10-24-2017, 03:40 AM
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2x4 will be fine. The only thing that will carry any real weight will be the legs. The tank actually needs no support in the middle. My 55s, 90 and 75 are on metal stands and you can see daylight between the stand's horizontal members and the rim of the tank.

The important thing is to have the tank rest on the wood corners and then it needs to carry down to wood to the floor. Never count on fasteners to support any weight at all.
Look at this build to see what I mean.
Pictures on post 3 in that thread.
https://www.plantedtank.net/forums/20...-works-me.html
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post #10 of 12 (permalink) Old 10-24-2017, 07:03 PM
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Quote:
Originally Posted by ChrisX View Post
Thanks. A few months ago I bought a commercial stand, and I figured with a 2x4 frame and using the prefinished MDF for exterior surfaces, it will look quite good. I have been meaning to take this desk to the landfill, so I might as well reuse it.

Jeff, the desktop is 1" MDF. The tank would be fully supported by the frame, this would just be for cosmetics.

Bump: In this stand design, why does the inner green beam not go to the top of the frame?

https://www.monsterfishkeepers.com/f...te-jpg.455260/
The inner green beam is just a nailing strip. It doesn't support weight. It is only there to fasten the vertical legs to. A 2x2 works just as good as a 2x4 there.

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post #11 of 12 (permalink) Old 10-24-2017, 09:04 PM
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so I've been wanting to build a custom stand myself. If you were doing this in a rack style...
Would you make cut outs on the corners of the 3/4" plywood on the middle rack so it would rest on both the side and long rails of the stand?
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post #12 of 12 (permalink) Old 10-25-2017, 01:03 AM
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so I've been wanting to build a custom stand myself. If you were doing this in a rack style...
Would you make cut outs on the corners of the 3/4" plywood on the middle rack so it would rest on both the side and long rails of the stand?
If I were doing a rack that was meant to be in a living area I would use 2x4 uprights and 2x3 horizontal runners.
I would cut dadoes into the 2x4 uprights to house the 2x3s. All nice and flat faces on the outside. Then I'd skin it with 1/2" hardwood plywood and stain it. I'd use moldings to hide the plywood edges. If I had a bandsaw I'd get 1x solid hardwood and resaw it in half and face it with that wood instead. No molding needed that way.
Here is the thread of a couple of my racks in the fish house. The 8' rack is 2x3 with the horizontals only rabbeted half way. The breeder rack is a full depth rabbet and would take a skin very nicely.

You get strength without having to have the carpentry skills to make the rack from only 3/4" plywood.

https://www.plantedtank.net/forums/12...ish-house.html

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