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Aquarium Stand - Pocket holes between dowels?

1907 Views 41 Replies 13 Participants Last post by  northwoodsman
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I'm building this stand for my aquarium. It's 3/4 Hickory ply. I've placed dowels top and bottom on the 2 side panels and then on the back panel, I drilled pocket holes every 6 inches on every side. The back sits inside the top, bottom, and 2 sides.
I had planned on doing 4 pocket holes on the left and right side panels between the dowels. Since the inside of the cabinet will be painted, once I plug the holes and paint, you will never see them. So the question is, will I gain any strength of the joint by adding the screws to a dowelled and glued joint? My plan is to glue and clamp up all along the joints with dowels.

Here are some pics of what I've put together:
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(Behind this front panel will be a stretcher made from 2 pieces of 3/4 ply glued and screwed together and then pocket hole screwed into the side panels. I'll then run screws through it into the front panel.)
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How big is the tank? Is it going to be filled with water? If it is I would use some type of framing not just plywood.
Yes, it's an aquarium, 80 gallon saltwater aquarium. If you've ever seen a commercial aquarium stand, they are usually MDF with melanine veneer and cam lock connections with some dowels. You would not believe they would hold up an aquarium but they do.
Many folks will use 2×4 frames with plywood because it's just easy to work with and not exactly necessary.
I was thinking the same thing. When I used to build tanks for buddy that has a reef tank business I always built a frame of 2×4. The structural part was somewhat separate from the pretty part.
Consider adding something in the corners. I know tank guys love space for pumps and sump .
Even a 2×2 gorilla glued in the corners is better then nothing.
Good Luck
I was thinking the same thing. When I used to build tanks for buddy that has a reef tank business I always built a frame of 2×4. The structural part was somewhat separate from the pretty part.
Consider adding something in the corners. I know tank guys love space for pumps and sump .
Even a 2×2 gorilla glued in the corners is better then nothing.
Good Luck

- Aj2
Ah, you got some experience with this. Cool. I'm a little fuzzy on the 2×2 idea. Is that running the length up the sides and back? Can't do that, sump won't fit. My research tells me that the main idea is prevent racking from side to side. The stand is all dry fit right now and no b screws in the back panel and it's solid when pushing on one side. I see no flex on the other.
well your looking at about 750-800lbs my friend. as in the movie jaws when they see the shark and says,your gonna need a bigger boat !!! well your gonna need a hell of a lot stronger stand my friend. what your making is a huge accident waiting to happen.id say scrap what youve done and re engineer. you need a strong frame for that much water plus weight of the tank.back to the drawing board.
well your looking at about 750-800lbs my friend. as in the movie jaws when they see the shark and says,your gonna need a bigger boat !!! well your gonna need a hell of a lot stronger stand my friend. what your making is a huge accident waiting to happen.id say scrap what youve done and re engineer. you need a strong frame for that much water plus weight of the tank.back to the drawing board.

- pottz
I can show you any number of stands built similarly that hold larger tanks than mine.
well your looking at about 750-800lbs my friend. as in the movie jaws when they see the shark and says,your gonna need a bigger boat !!! well your gonna need a hell of a lot stronger stand my friend. what your making is a huge accident waiting to happen.id say scrap what youve done and re engineer. you need a strong frame for that much water plus weight of the tank.back to the drawing board.

- pottz

I can show you any number of stands built similarly that hold larger tanks than mine.

- Chichas
not in my house you wont.if your gonna rely on plywood and pocket screws alone,good luck. please post some pic's of those stands your talking about.
well your looking at about 750-800lbs my friend. as in the movie jaws when they see the shark and says,your gonna need a bigger boat !!! well your gonna need a hell of a lot stronger stand my friend. what your making is a huge accident waiting to happen.id say scrap what youve done and re engineer. you need a strong frame for that much water plus weight of the tank.back to the drawing board.

- pottz

I can show you any number of stands built similarly that hold larger tanks than mine.

- Chichas

not in my house you wont.if your gonna rely on plywood and pocket screws alone,good luck. please post some pic s of those stands your talking about.

- pottz
You don't read thoroughly, do you?
well your looking at about 750-800lbs my friend. as in the movie jaws when they see the shark and says,your gonna need a bigger boat !!! well your gonna need a hell of a lot stronger stand my friend. what your making is a huge accident waiting to happen.id say scrap what youve done and re engineer. you need a strong frame for that much water plus weight of the tank.back to the drawing board.

- pottz

I can show you any number of stands built similarly that hold larger tanks than mine.

- Chichas

not in my house you wont.if your gonna rely on plywood and pocket screws alone,good luck. please post some pic s of those stands your talking about.

- pottz
Here is an example of a commercial stand, made with MDF.

https://www.reef2reef.com/threads/new-build-red-sea-reefer-peninsula-500.344388/
I think that the plywood sides and back will be pretty strong, though the front corners need more support, IMO. If you think about it, four 2×4s in the corners are less wood than the 3 sides of plywood as long as the joinery prevents them from bowing out our racking. The dowels and pocket screws (and glue) on the back panel will prevent that. My concern is with the top and front apron, stretcher or whatever that header is called. I think that doubling it up makes it strong enough but I would want support under it, not just attached to the front. I probably would have put it under the top, like the apron of a table and if you add a vertical strip under each end on the front, that adds more support and also makes the front corners stronger (attach them to the sides with pocket screws). I built plywood legs for my "assembly/outfeed table (see below) and the legs are plenty strong. I have had 400-500 lbs on it and it seemed rock solid. It also would not hurt to put a piece under the top in the middle connecting the front header to the back. My 2-cents.

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That particle board one has a little more support to it. It has the one piece in the middle. Like Nathan mentioned it needs a little more in the front to keep it from racking.
I owned a small tropical fish shop with over a 100 tanks, I built many stands and even my own glass tanks.
I would not trust that structure with 80 gallons of water on top.
Have you considered centre sag? Many tanks on home made stand crack across the bottom because the base sags and the entire weight is on the four corners.
I think that the plywood sides and back will be pretty strong, though the front corners need more support, IMO. If you think about it, four 2×4s in the corners are less wood than the 3 sides of plywood as long as the joinery prevents them from bowing out our racking. The dowels and pocket screws (and glue) on the back panel will prevent that. My concern is with the top and front apron, stretcher or whatever that header is called. I think that doubling it up makes it strong enough but I would want support under it, not just attached to the front. I probably would have put it under the top, like the apron of a table and if you add a vertical strip under each end on the front, that adds more support and also makes the front corners stronger (attach them to the sides with pocket screws). I built plywood legs for my "assembly/outfeed table (see below) and the legs are plenty strong. I have had 400-500 lbs on it and it seemed rock solid. It also would not hurt to put a piece under the top in the middle connecting the front header to the back. My 2-cents.



- Lazyman
Thanks Nathan. If you look at 5th pic that shows the front top panel, I mentioned doing your idea of doubling up a stretcher behind that and it would be directly under the top. Good idea!
I did also consider adding a center upright brace once the sump is in. I like that idea.I'm on the fence about that. It has some benefit other than supporting the front side as it will also block light from escaping the gap between the doors. There's a light that will be on inside the cabinet during the night and it would be nice to block that.
That particle board one has a little more support to it. It has the one piece in the middle. Like Nathan mentioned it needs a little more in the front to keep it from racking.

- corelz125
Racking or sagging?
I owned a small tropical fish shop with over a 100 tanks, I built many stands and even my own glass tanks.
I would not trust that structure with 80 gallons of water on top.
Have you considered centre sag? Many tanks on home made stand crack across the bottom because the base sags and the entire weight is on the four corners.

- sunnybob
+1
I owned a small tropical fish shop with over a 100 tanks, I built many stands and even my own glass tanks.
I would not trust that structure with 80 gallons of water on top.
Have you considered centre sag? Many tanks on home made stand crack across the bottom because the base sags and the entire weight is on the four corners.

- sunnybob
Unclear on this. You're referring to glass tanks? Glass only require support along the edge of the aquarium. Acrylic requires support across the entire bottom? Do you have any thoughts on the way commercial stands are constructed? Here's an example:

https://www.reef2reef.com/threads/new-build-red-sea-reefer-peninsula-500.344388/
That particle board one has a little more support to it. It has the one piece in the middle. Like Nathan mentioned it needs a little more in the front to keep it from racking.

- corelz125

Racking or sagging?

- Chichas
these words confuse you ? oh boy!!!!
Sunny Bob is correct. I remember tanks need support in the corners. I've set up lots of the stands I made and always made sure the surface that the tank sits was flat so the stand would not twist. A twist will wreak a Acrylic tank faster then a glass one.
Care should be taken for both
I remember the glass tanks that we picked up in San Diego had a floating bottom.
2×2 vertical in the corners is what I was thinking.
Good Luck
You are completely wrong about glass only needing corner supports. Glass is very weak if subjected to bowing pressure.
You might be thinking about the weight of water being evenly spread over the entire surface, but what about rocks and gravel and sand? All of that weight is directed downwards only. A large rock placed centrally in any tank will result in the base bowing.

I have made hundreds of glass tanks, in thicknesses up to 10 mm plate glass, and I would not allow ANY of them to stand on an unsupported flat surface.
An Aquarium shop should sell a 12 mm thick polystyrene (styrofoam) sheet for under the tank to absorb any imperfections. A single grain of grit under a large tank will exert enough localised upwards pressure to crack the glass. by the same token, if its a large tank, a solid full sized piece of polystyrene should not be used, as it will compress at the edges but not in the middle, causing an upwards bulge that will also split an all glass tank base.

You of course are at liberty to completely ignore all the good advice you have been given if it doesnt agree with your inexperienced perceptions.
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