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Building Co-op Style Racks for My Fish Room


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I visited the store for the first time last March and I really like the design of their racks.  As I prep to build my own fish room rack, I am going to build from and modify that design.  I'll track my progress in this thread.

First up, research.  Here are all of the links I found covering the building this sort of rack (and variations).

Achieve the open front of the Co-Op rack for ease of access for maintenance and access to stock.

When finished, this rack will have three shelves as follows:

  • Shelf 1: Top. Holds seven 20Ls.  Because these tanks are smaller than those on Shelf 2, the cleat method cannot be applied. Instead, this will be a traditional shelf using the dado cut method (see above) with tanks being supported by the full shelf, not just cleats.
  • Shelf 2: Middle. Holds one of the following configurations:
    • One 125G and two 75G
    • One 125G and four 40B
    • Four 60B
  • Shelf 3: Bottom.  For now, just storage.  But may be used to house four 50g lowboys for plant farming.


  • Rack Dimensions
    • Width: 17ft 8inches
    • Height: 7ft 10 inches
  • Lumber
    • Uprights: 2x6
    • Cleats: 2x4
    • Crossmembers: 2x4
  • Rack Stability: The rack will not be free-standing. Instead, the back and sides of the rack will be attached to the studs in the wall, almost like a built-in entertainment center.  So, the wall attachment will create more stability on all sides while transferring some weight to the walls.
  • Tank Style: All tanks are rimmed.  All but the 125G are Aqueon. 125G is Marineland.


  1. Without modification, can Cory's cleat design hold the 40Bs and up?  What is the upper size limit?
    • If anyone has photos of large tanks being supported by the cleat method, I would love to see them.
  2. Assuming there is some size limit, could that be solved by adding a crossmember to support the back of the tank while leaving the front of the tank open? 
  3. Could building the back of the rack using the dado cut method outlined in research help that even further?
  4. Am I missing anything?

Thanks in advance for any comments or advice.  I'll post pictures as I build.



Edited by SunkenScenes
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On 5/24/2023 at 4:15 AM, SunkenScenes said:

Without modification, can Cory's cleat design hold the 40Bs and up?  What is the upper size limit?

Cory mentioned in a livestream or a vid that the method has worked with aquariums up to 75 gallons. @Cory @brandonnaturally

On 5/24/2023 at 4:15 AM, SunkenScenes said:

Thanks in advance for any comments or advice.  I'll post pictures as I build.

Can't wait to see them!

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Does anyone know of a simple formula or calculator for determining load capacity for a span of dimensional lumber?

I assume we would treat any lumber (2x4, 2x6) as floor joists in a very small floor.  I am planning to share my design file and calculations for others to use as a shortcut to building their own racks, I would like to give accurate information on load bearing capacity and, as extension, tanks that can work in a given design.

The immediate concern is the top shelf (Shelf 1) for this project.  To achieve the open structure like the Co-Op rqcks with larger tanks on the bottom, I need to safely span the the larger tanks on Shelf 2.  Those potential spans (tank + support) are:

  • 125g72.5" + 3" = 75.5" (6' 3.5")  — 1400 lbs min
  • 75g48.5" + 3" = 51.5" (4' 3.5") — 850lbs min
  • 60B — 48.5" + 3" = 51.5" (4' 3.5") — 660 lbs min
  • 40B —  36.5" + 3" = 39.5" (3' 3.5") — 460 lbs min
  • 20L 30.5" + 3" = 33.5" (2' 9.5") — 225 lbs min

PS: Tank dimensions an weights found at CC Aqua.

With all of the above in mind,   I figure I'll almost certainly go with this configuration:

  • Shelf 1: 20L x 7
  • Shelf 2: 60B x4

Which mean 5 uprights:

  • One on either side, attached to wall
  • Three span supports, one between each of the 60Bs.
  • 48.5"-51.5" = Max span between span supports.
  • 450lbs = Minimum weight supported by each span (2 x 20L)

Everything I am finding online makes me think I should be fine.  But would like someone who really knows the math to confirm.

Just added a drawing of how I am thinking of laying out the 2x4s for Shelf 1.


Edited by SunkenScenes
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So, I tried a lot of the free load calculators on the Internet and all of them left something out to get you to subscribe.  So, I gave ChatGPT a try.


What is the load-bearing capacity, in pounds, of wooden 2x4 beam which is 52 inches  and long oriented with the wider face as its vertical height?


To calculate the load-bearing capacity of a wooden 2x4 beam with a length of 52 inches and oriented with the wider face as its vertical height, we need to use the formula provided earlier. Here are the calculations:

Width of the beam (b): 3.5 inches
Height of the beam (h): 1.5 inches
Length of the beam (L): 52 inches
Allowable stress for softwood (S): 1,000 pounds per square inch (psi)

First, let's calculate the moment of inertia (I) using the formula:

I = (b * h^3) / 12

I = (3.5 * 1.5^3) / 12
I = 0.984375 square inches

Now, we can calculate the maximum load-bearing capacity (W) using the formula:

W = (5 * S * I) / (4 * L)

W = (5 * 1,000 * 0.984375) / (4 * 52)
W = 2,421.875 pounds

Therefore, the load-bearing capacity of the wooden 2x4 beam in this scenario is approximately 2,421.875 pounds.

Can anyone confirm the math?

If so, the next thing I am going to ask ChatGPT is:

What is the airspeed velocity of an unladen swallow?

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