Cinderblock tank rack?

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MoshJosh

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Have posted before about making a tank rack from 2X4s. Was intending to hold 3 20 or 29 gal tanks, but now I’m thinking bigger. . . Now I still plan on making the smaller rack for breeding but will need something for grow out (also want to keep some big fish for the enjoyment). Was thinking 2 tanks per rack anywhere from 55-125 gal. . . Saw some videos (specifically the aquarium coop one) on cinderblock racks. Would blocks and 2x4/4x4 work for such big tanks? Is stacking the cinderblocks that high safe without somehow securing them? Maybe a big tank on the bottom (with center supports under) and a 55 above?

Mind you this is all pretty far off but. . . Knowledge is power right?
 

kallililly1973

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I can't vouch for a big tank on cinders but my 29-20 and 10 are all on cinders. and if i were to set up a large tank i would definitely go the cinderblock route again without a doubt. For my 29 and 20 i used 8 blocks and 2 pieces of 1/2" plywood for each tank. I put a single cinder then ran the plywood across then placed the other 3 on each side and added the plywood. For my 10 all i did was a single pile of 4 cinders with a piece of plywood. I think if i did a large tank like your tanking i would uses 3-4 piles of cinders 4 high for each pile and then top it with a couple 2x10's butted together for the tank to rest on.
 

david1978

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Well considering we build houses out of cement blocks they will hold a tremendous amount of weight. I even use then under my jack when i jack up my 7500 pound pickup.
 

Blondeath

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Won’t the ply wood bow overtime?
 

david1978

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Plywood does but with the short tanks its not an issue since its more to just level things and not actual support. Now with the bigger tanks you would want to use 2x8 or 2x10 boards which will also bow if not properly supported but will require much less under support.
 

qquake2k

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I would think 4x4's or 4x6's wouldn't bow like 2x4's or 2x6's might.
 

david1978

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Over time any board will especially if it gets damp.
 

JayH

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The thing I would worry about is sag in the 2x4s. They're intended to bear weight along their length, not across the narrowest dimension. For larger tanks you might want to think about using 2x4s on edge with a piece of plywood laid on top and screwed in place to keep the 2x4s aligned. That would put the weight across the longer cross dimension and also give you a flat surface to put the tank on. I'd think 1/2" plywood would be adequate.
 

david1978

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Basically an engineered beam design.
 

saltwater60

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I’d do 4 by 4’ or 4by 6’s with that size tank. I’m doing a tank and I’m doing 4by 4’s. It will be a 75, two 50’s or a 125. Still deciding. I’m not hung the 4by 4 posts not doing cinder blocks. I don’t trust cinder blocks long term. I’ve seen too many crack in my day. Yes we build houses out of them as mentioned but they are used differently.
 

david1978

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Building your own engineered beam would be far superior to 4x6's. Basically 2 2x10's then plywood them 2x10's on top. It gets the wood grain running in different directions. Screw it and glue it all together. To biw it all but has to rip the plywood apart.
 

saltwater60

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david1978 said:
Building your own engineered beam would be far superior to 4x6's. Basically 2 2x10's then plywood them 2x10's on top. It gets the wood grain running in different directions. Screw it and glue it all together. To biw it all but has to rip the plywood apart.
2x10’s won’t fit into cinder blocks though. Many ways to do it. Steel beams are great and can be powder coated.
4 by 4 horizontally should be plenty of strength and estimate to hold over 2 tons per board. And about 9,000-10,000 lbs compression load rating.

https://www.worthview.com/much-weight-can-4x4-support-horizontally/
 

JayH

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saltwater60 said:
4 by 4 horizontally should be plenty of strength and estimate to hold over 2 tons per board. And about 9,000-10,000 lbs compression load rating.

https://www.worthview.com/much-weight-can-4x4-support-horizontally/
I'm not sure I'd trust the numbers from that article. I've read in several places that a 8' 2x4 will safely support 800 pounds vertically. I've not seen numbers for horizontal support, but given this application is using them with the weight passing through the narrowest dimension, I have to think it's a LOT less than 800 pounds.

david1978 said:
Basically an engineered beam design.
I wouldn't have thought to put it that way, but, yeah, that's what it is. I was only thinking plywood on the upper edge, but it would be much better to sandwich the 2x4s between plywood sheets. That would almost eliminate the side load on the 2x4 fasteners and greatly improve the rigidity of the beam.

Even with all this enhancement -- plywood, glue, stainless steel screws -- cost would still be significantly less than commercial shelving capable of safely supporting the same weight. It would be more work and would require tools, though nothing exotic.
 

coralbandit

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I don't think the wood matters much ?
If both sides [ all 4 corners] of tank are supported by the block you are set ..Even on a 6 foot tank ..I might put wood over block to make it smooth?
When you talk about how to make an engineered beam what do you think happens when you silicone glass together ?
The bottom of tanks do not bow . That was a PERIOD ..If they did then the caulk would fail ???
My 180 g rest on 3 1/2 inches on each end and has no support in middle ..Only like 10 years so still testing ...
 

saltwater60

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JayH said:
I'm not sure I'd trust the numbers from that article. I've read in several places that a 8' 2x4 will safely support 800 pounds vertically. I've not seen numbers for horizontal support, but given this application is using them with the weight passing through the narrowest dimension, I have to think it's a LOT less than 800 pounds.


I wouldn't have thought to put it that way, but, yeah, that's what it is. I was only thinking plywood on the upper edge, but it would be much better to sandwich the 2x4s between plywood sheets. That would almost eliminate the side load on the 2x4 fasteners and greatly improve the rigidity of the beam.

Even with all this enhancement -- plywood, glue, stainless steel screws -- cost would still be significantly less than commercial shelving capable of safely supporting the same weight. It would be more work and would require tools, though nothing exotic.
First I said 4x4’s not 2x4’ and yes I could see 2x4’s supporting that vertically because they will now sideways at the 2” width.
 

JayH

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coralbandit said:
I don't think the wood matters much ?
If both sides [ all 4 corners] of tank are supported by the block you are set ..Even on a 6 foot tank ..I might put wood over block to make it smooth?
When you talk about how to make an engineered beam what do you think happens when you silicone glass together ?
The bottom of tanks do not bow . That was a PERIOD ..If they did then the caulk would fail ???
My 180 g rest on 3 1/2 inches on each end and has no support in middle ..Only like 10 years so still testing ...
At the risk of stating the intuitively obvious, glass is not wood. The support structure for the bottom of the tank is also different. It's joined on all four edges to other pieces of glass that transfer the load from the bottom all over the place. Compare this to a couple 2x4s supported only on the ends, with a heavy weight in the middle of the span. Different structure and weight distribution entirely.

With the racks that Cory built, the ends of the tanks are NOT resting on the cinder blocks. The weight of the tanks is supported entirely by the wood. In his setup he's talking about putting two 20H tanks in between each cinder block column. That leaves one end of each tank in the center of the span. Certainly, all of this weight is eventually transferred to the cinder blocks, but it can deflect the wood, particularly toward the center of the span.

There's a shelf in one of my kitchen cupboards that's made of 5/8" plywood. It has had a set of china on it for several decades. There's a distinct bow in the center of that shelf. That's with plywood with alternating grain and maybe 50 pounds of dishes on top. If that was a 2x4 with the weight going through the narrowest dimension I'm pretty sure I'd be seeing an inch or more of deflection. I can't imagine what it would look like if that was 500 pounds of aquarium on top.
 

JayH

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saltwater60 said:
First I said 4x4’s not 2x4’ and yes I could see 2x4’s supporting that vertically because they will now sideways at the 2” width.
I understand that you said 4x4s, but a 4x4 is the same as two 2x4s sandwiched together. I found some online references that seem a bit more authoritative than the article you referenced that was focused on backyard swings and tree houses. It claims a load rating of 5000 pounds vertically for stud grade 4x4s at 8 foot length. There was no indication of how much weight it could withstand without deflection when placed horizontally, but I have to think it's considerably less than 5000 pounds.

Based on this, I have to think that what Cory did with 2x4s resting on their wide edge is not a particularly good idea. Over time it's very likely the wood will begin to sag in the center. The fact that the aquarium weight is born entirely by the four corners of the tank actually makes the situation worse since it means the center beam is essentially doing nothing. All the weight is born by the two outer beams.

Creating an engineered beam out of 2x4s and plywood would change this, allowing all three beams to share equally in transferring the load to the cinder blocks. Changing the orientation of the beams so the weight is transferred through the wider dimension also will greatly increase the stiffness of the engineered beam. It will chew up a few more inches of vertical space, but that seems a fair trade to me.
 

saltwater60

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JayH said:
I understand that you said 4x4s, but a 4x4 is the same as two 2x4s sandwiched together. I found some online references that seem a bit more authoritative than the article you referenced that was focused on backyard swings and tree houses. It claims a load rating of 5000 pounds vertically for stud grade 4x4s at 8 foot length. There was no indication of how much weight it could withstand without deflection when placed horizontally, but I have to think it's considerably less than 5000 pounds.

Based on this, I have to think that what Cory did with 2x4s resting on their wide edge is not a particularly good idea. Over time it's very likely the wood will begin to sag in the center. The fact that the aquarium weight is born entirely by the four corners of the tank actually makes the situation worse since it means the center beam is essentially doing nothing. All the weight is born by the two outer beams.

Creating an engineered beam out of 2x4s and plywood would change this, allowing all three beams to share equally in transferring the load to the cinder blocks. Changing the orientation of the beams so the weight is transferred through the wider dimension also will greatly increase the stiffness of the engineered beam. It will chew up a few more inches of vertical space, but that seems a fair trade to me.
I agree if they are resting on the wide edge meaning the tank is sitting on the 4”side that’s not a good idea at all.

Also a 4x4 is certainly stronger than two 2x4’s sandwiches together.

Also part of it is how it is put together and designed. I had a 55 gallon tank on a 2x4 built stand for years. Held up great.
If you look at the 125 stand at the LFS you’ll see they are not made with anything thicker than 1/2” or maybe 3/4” wood. It’s all about design.

Again I agree 100% placing any weight on the 4” side of a 2x4 or even 2x6 is a bad idea.
 

kallililly1973

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This thread is getting deep :) I made my 55 tank stand out of 2x4's and its held perfect for close to 3 years without a hitch. It's sad that the lumber now a days isn't truly what it should be. A 2x4 is technically a 3.5 x 1.5" same for 2x6's 2x8's and so on..
 

david1978

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kallililly1973 said:
This thread is getting deep :) I made my 55 tank stand out of 2x4's and its held perfect for close to 3 years without a hitch. It's sad that the lumber now a days isn't truly what it should be. A 2x4 is technically a 3.5 x 1.5" same for 2x6's 2x8's and so on..
Not ruf cut from the lumber yard. Actually horizojtally 2 2x4 sandwiches together will be stronger then a 4x4 since your separating the grain of the wood and it would have to stretch one board and shrink the other.
 
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