10” multi-tank stand need design help

Azure Scolymia · May 19, 2020

I am basing my design roughly on rocketengineer‘s design posted here:

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My goals are slightly different than most people’s. In most cases, people are building a stand for a specific tank. I have tanks in mind for this stand, but I want to build in enough strength, that I can change my mind later. I know how this hobby is. I want to be able buy different tanks later without having to replace the whole stand. The current plan for this stand is to put 2 seapora 80 gallon frag tanks 24x48x18 and a recirculating skimmer on the top and two 75 gallon tanks in the bottom. My dream though is to be able to put 2 feet of water anywhere on top and have it work out ok. In order to achieve this goal, I plan to incorporate a few changes. Please excuse the crudeness of my drawing.

I want to add a vertical support (A) in the center for the front and the back. This will allow me slide a 48” tank in the front. How big should this support be? 2x4?

Since the tanks on the top will not line up with the edges of stand I plan to add back-to-front supports (B). I am planning to use 2x4. How many should I use?

Since the tanks on the bottom will not line up with the edges of stand I plan to add back-to-front supports (C). I am planning to use 2x4. How many should I use?

I plan to use plywood (Shaded in pencil) to distribute the weight to the supports. How thick should this plywood be?

How big should the upper rails and upper ends (Red and yellow in the first picture) be? 2x8?

The thing I don’t know how to deal with is the tendency for the top to walk away from the bottom. I had not planned putting plywood on the front, back, or side faces. This is to facilitate easy plumbing. Is there something I can do to mitigate this risk? Are plywood faces the only option?

andrewey · May 20, 2020

Hopefully someone can weigh in here that has practical engineering experience. If you want to put 2 feet of water on top, that's 300 gallons your stand has to support. If I were building this stand, I would certainly put more than one vertical member to break up a 10' run (your piece A), but hopefully someone who builds these will know what the correct number is.

In addition, I would think you would want quite a few "B"s. Since you mentioned putting a 4' long on the stand, I'm assuming you would likely center the aquarium. As such, it would only be resting on the single middle support halfway through the tank, even if you included two more pieces to split the difference. Therefore, you would have to add more horizontal "B"s to ensure that they weren't every 30".

Sorry I can't be of more help- my gut is to use a ton of more lumber for piece of mind/support, however I don't want to throw out crazy numbers of supports or what size wood I would use, as I've never built a stand of this size.

Azure Scolymia · May 21, 2020

andrewey said:
Hopefully someone can weigh in here that has practical engineering experience. If you want to put 2 feet of water on top, that's 300 gallons your stand has to support. If I were building this stand, I would certainly put more than one vertical member to break up a 10' run (your piece A), but hopefully someone who builds these will know what the correct number is.

In addition, I would think you would want quite a few "B"s. Since you mentioned putting a 4' long on the stand, I'm assuming you would likely center the aquarium. As such, it would only be resting on the single middle support halfway through the tank, even if you included two more pieces to split the difference. Therefore, you would have to add more horizontal "B"s to ensure that they weren't every 30".

Sorry I can't be of more help- my gut is to use a ton of more lumber for piece of mind/support, however I don't want to throw out crazy numbers of supports or what size wood I would use, as I've never built a stand of this size.

I appreciate your gut reaction. As for the vertical supports (A) I was surprised at the following suggestion from the quoted thread:

“125g-240g: For tanks 72" long, I recommend a 2X8 top frame to span the full width of the tank without a center leg.”

Now, if we think about my design as two 60” tank stands holding up to 150g apiece, that seems to fit right into those figures. I know it doesn’t work exactly like that, but it makes me think I am in the right ball park.

As for B and C, my thoughts were the same as yours. I didn’t know how many, so I drew “something.” It was mostly to help communicate what I meant. After further thought, I decided I wanted an even number so that they do not interfere with A. I also wanted them to be at most 24” apart. That landed me on 6. This brings me to my current design.