Square Hole in Top of Stand Placed 1/4" From Edge of Bottom Frame of Tank?

[SkyReef]

Short Question:

Is it safe to have the bottom rim of a tank lie a mere 1/4" inch from the edge of a square hole (5"x5") that was cut in the plywood top of a stand? Even if the square hole exposes the "end" stud beneath the hole, somewhat?

Long Explanation and Pictures:

A. The Tank and Stand

• I have an 80-gallon Deep Blue frag tank;
• The top of the tank has no plastic frame, but the bottom of the tank does have one;
• The tank has a corner overflow, in which two holes are drilled through the bottom of the tank;
• I am using a Rocket-Engineer design, DIY Stand;
• The stand has 2"x6" studs for the top frame;
• I have affixed a sheath of 3/4" plywood to the top of the stand;
• The tank sits on the plywood, which rests on the frame;
• The portion of the stand that lies to the right of the tank, extends 12 inches, beneath which is an extra compartment in the stand; and
• Here is a picture of the tank and stand, still under construction:

Photo: Note that the tank sits atop the left portion of the stand, with a right-side cabinet compartment beneath
the portion of the stand where there is no tank. This may help stabilize the sheathing over the stand, to compensate
for the plywood square hole that extends across the "airspace" of the "end" stud.
___________________________

B. The Square Hole in the Top of the Stand

• I have cut a 5" x 5" square hole in the plywood of the top of the stand, to allow the the corner overflow's drain pipes to pass through to the sump below;
• The plywood-window is cut beneath the right edge of the tank;
• Thus, most of the tank (about 43 inches of the the length of the tank) lies to the left of the square hole, supported by the 2x6" top frame beneath the plywood, which has no other holes in it;
• The plastic frame situated at the short "end" of the tank lies a mere 1/4" to the right of the 5" plywood square hole; and
• Here are some pictures of the square hole and the exposed end-stud:

Photo: Note the tan wood "line" in the picture above, to the right of the top bulkhead:
that is the exposed "end" stud below the plywood. This shows that the bottom rim of
the tank is resting on the plywood with a 1/4" to spare, but beyond that to the left, the
plywood is "vacated" off the stud below by 1 inch, leaving only 1/2 inch of the stud covered
by the plywood. This only occurs for 5 of 24 inches of the end run, i.e., the length of
the square hole. Above the square hole--or to the north of it--the plywood closes back up again,
over the entire area of the plywood top.
___________________________

A close up of the square hole:

Photo: Here you can better see the exposed "end" stud below the plywood and the right edge of the plywood,
square hole. To the right of this square hole, 1/4-inch to the right, is where the bottom brace of the tank
rests, on the plywood. So it is fully supported by contact with the plywood there.
___________________________

Here is a view from underneath the tank:

Photo: Here the view of the square hole reveals it recedes off the stud of the "end" stud, for the length of
the square hole or 5 inches, but the plywood closes back up again to the left of the hole, providing
sheathing stability everywhere else for the weight of the tank.

___________________________

C. Bottom Line

• I am guessing that this is okay because the actual contact point of the plastic frame is in contiguous contact with the plywood at all times;
  
• I imagine this is fine because, if you think about it, the entire outside perimeter of many tanks comes right to the edge of the stand--without even a 1/4" of plywood support extending beyond that perimeter, which we have here to the right of the square hole;
  
• But I would appreciate your thoughts because I could be quite wrong;
  
• Is this a safe move, or should I re-cut the top, to close up the exposure of plywood now existing over the "end stud"?; and
• In case you're wondering, I cut the square hole this way because it is easier to screw and unscrew the drain lines from the bulkheads in this area, should I ever need to do that.

 

[Ron Reefman]

IMHO you are good to go.

I have a 65g shallow reef (4'x2'x14") that I made and is rimless. It sits on a stand very similar to yours and with a hole at the end almost exactly like yours. Mine has been set up and running for 5 years now and zero issues.

Your tank sit's on the frame, not the bottom glass (like mine does) and that should make it even safer. Just make sure the stand is flat on the floor and the top of the stand is flat corner to corner.

 

[der_wille_zur_macht]

I agree. If the stand is true there's no problem. Typical way-too-strong overbuilt 2x lumber stand, it'll be fine. The only concern I would have is making sure that exposed plywood endgrain is well sealed from moisture.

 

[SkyReef]

IMHO you are good to go.

I have a 65g shallow reef (4'x2'x14") that I made and is rimless. It sits on a stand very similar to yours and with a hole at the end almost exactly like yours. Mine has been set up and running for 5 years now and zero issues.

Your tank sit's on the frame, not the bottom glass (like mine does) and that should make it even safer. Just make sure the stand is flat on the floor and the top of the stand is flat corner to corner.

Thanks, Ron. Very helpful. But I want to understand your responses better:

• When you say make sure the stand is flat on the floor, do you mean make sure it is level everywhere, including by use of shims, if necessary? If so, I definitely intend to do that, and the stand will sit on a carpeted floor, which hopefully will help here; and
  
• When you say make sure the top of the stand is flat corner to corner, do you mean that the top frame should have no "high" points or waviness to it along the top edge of the top 2x6 stud frame?
  
• If so, then I fail here:
  • I have belt-sanded the top, 2x6 stud frame to smoothen out the peaks and valleys occurring there;
    
  • But after considerable effort, I see that it is not absolutely without minor unevenness;
    
  • I intended to "fix" this by attaching the top plywood frame to the top stud frame by screws and glue;
  • I had hoped that the glue would act as a viscous "leveler" of sorts;
  • How perfect with non-waviness does the top rim of the 2x6 stud frame need to be?; and
  • Won't the plywood sheath help buffer any minor flaws of waviness on the top stud frame, that lies beneath it?

I agree. If the stand is true there's no problem. Typical way-too-strong overbuilt 2x lumber stand, it'll be fine. The only concern I would have is making sure that exposed plywood endgrain is well sealed from moisture.

Thanks, Der Willie. Also helpful to know. I will be painting the entire wood stand with Rustoleum, flat white paint, to prevent moisture seepage into to the grain of wood. Hopefully, that should suffice.

 

[ClownNut]

you want to reverse your bulkheads. otherwise, you won't be able to remove them once you have stuff start to grow on the threads.

 

[Lsufan]

Like Ron & willie mentioned, the hole is fine. The plywood isn't helping support the thank, that is what the frame is doing. The plywood is really only helping to keep the stand square & from twisting.

The bottom trim really needs to be making contact everywhere. If it is only a very small gap for only a inch or two it may be ok, but if it's worse then that it can cause issues. If it is actually a high spot so the tank wants to wobble then u really need to do something about it to fix it.

I agree with clownutt on the bulkheads, they can work how u have them but I always like to put the flange on the wet side unless I just don't have that option.

 

[SkyReef]

Thank you, Lsufan and ClownNut. I've been doing more sanding on the frame, and everything is more even. I'm feeling quite confident it will be in a very good specs range. I'll also flip the bulkheads around, nut-side down, flange-side up.

 

[Ron Reefman]

Wow! I didn't even notice the bulkheads. Yeah, flip them over. You can even enlarge the square hole in the stand to have more room to get a wrench in there if you should ever need to.

When you say make sure the stand is flat on the floor, do you mean make sure it is level everywhere, including by use of shims, if necessary? If so, I definitely intend to do that, and the stand will sit on a carpeted floor, which hopefully will help here.

Yes. Given you will be on carpet, that can help. I live in Florida and our entire house is tile. It's not uncommon at all that some tiles stand up a bit proud (higher) than other tiles on the floor.

When you say make sure the top of the stand is flat corner to corner, do you mean that the top frame should have no "high" points or waviness to it along the top edge of the top 2x6 stud frame?

Use a long straight edge and see that the surface the tank will sit on is straight. Small imperfections are less important than big long dips or rises that will impact long sections of the tanks frame. And that corner to corner diagonally is level. Remember, the tank sits on the plastic frame, not on the bottom glass. So most of a plywood top isn't an issue.

You don't need perfection here, but the better you can make it, the less likely you'll have any issues downstream. The stand can be built like tank, but if the corner to corner diagonal isn't level, the stand is twisted and the tank won't like that over the long haul. A friend had a front glass on a 220g tank crack diagonally after sitting for months due to a twisted stand.

 

[SkyReef]

Thanks, Ron. Your detailed answers help out a lot. Will do.