gap between tank and stand

[dougdstecklein]

I just finished building the support frame for my 90 gallon aquarium(48"x18"). I placed the tank on the stand and there is a gap between the tank and the stand slowly starting from the center(lengthwise) and increasing to an 1/8" on the left side of the tank. Is it better to shim underneath that side of the tank or leave it alone? My thought is once the water is added, the weight of the tank will fix the crown in the 2x4s and the weight will be distributed evenly. If I shim, I am worried I will then be left with a gap in the center of the tank. Any advice?

[CrazyEyes]

sytrofoam.

[billdogg]

If the top of the stand is not flat and level, fix it. And NOT WITH STYROFOAM!!!!

If you cannot plane it flat, a sheet of 3/4" plywood will work just fine - you can safely shim between the plywood and the frame of the stand. You can NEVER shim between the tank and the stand. It will create stress points and the tank will, sooner or later, fail.

hth

[dougdstecklein]

I guess I will try the plywood with shims underneath. Fix it right while I still can. Damn crap lumber.

[sleepydoc]

+1 fix it now. Not with styrofoam but by making sure the top is flat and level.

This is one of the hazards of using two-by lumber for a tank; it is often slightly cupped/warped/bowed. Better to catch it now than after your tank has sprung a leak.

[fishgate]

I had the exact same issue but I put a piece of 3/4 plywood under the tank and then put a few shims between the plywood and the crappy home depot 2x4s. It is perfectly level now with no gaps.

[dougdstecklein]

Ok, I spent a few hours today trying to straighten the 2x4s. I only have a 1/16 of an inch gap in a few spots. Is this acceptable? Or should I still do styrofoam or plywood?

[fishgate]

100% do plywood. It does wonders for stand/tank stability. 1/16 is a lot of stress on the joints. And the stand will only twist more. The plywood will help to stabilize the stand. HD will cut it the exact size you need it too.

[CrazyEyes]

Okay lol. I was always told to use styrofoam and have used it and seen it used on several tanks but I guess it doesn't work.

[bigfish14]

Originally Posted by CrazyEyes

Okay lol. I was always told to use styrofoam and have used it and seen it used on several tanks but I guess it doesn't work.

I heard the same thing about a year ago when I was setting up my first tank, so I went ahead and used styrofoam to provide a nice flat surface for my tank. However, I am recently learning that the styrofoam causes the tanks to lean in a certain direction over time. This had me thinking, so I checked my tank and sure enough it is leaning towards the back wall now. Luckily it will be coming down in a couple weeks because I am moving. I am using plywood on my new stand for my new 20 gallon tank.

[CrazyEyes]

Weird. I've always had people suggest it. Ohwell.

[sleepydoc]

A thin piece of foam should be used under a rimless tank to prevent point loading from pieces of sand, etc that would potentially stress and crack the bottom panel of the tank.

Foam should not be used under rimmed tanks, and never be used to compensate for an uneven stand. If you think about it, the foam is an even thickness and density. Why would you expect it to compress more at one end than the other?

[uncleof6]

Cure for out of whack stand:

Styrofoam, rigid foam, what have you: NO.

Plywood on top of out of whack frame: NO. They plywood is a lot less "rigid" than the lumber used for the top of the stand. Why would it be thought that the plywood would straighten out the top frame? It won't.

Shims under plywood: NO. Less stable than proper repairs.

Proper fix: Plane the top rim of the stand flat and co-planer. It has a hump in it--the crook is facing up rather than down--a construction error, that no one ever discusses. The only place you use shims is UNDER the stand, to correct an out of level condition with an otherwise flat and co-planer top rim.

Alternative fix: rebuild the stand, this time making sure the "crook" faces down, and the corners are co-planer. A dip in the middle is not the issue that a hump in the middle is.

What ever you choose to do, is up to you. I just wanted you to know the correct answer, not the standard shortcut "fixes," that are not fixes just because a lot of people "are doing it."

[fishgate]

Originally Posted by uncleof6

Cure for out of whack stand:

Styrofoam, rigid foam, what have you: NO.

Plywood on top of out of whack frame: NO. They plywood is a lot less "rigid" than the lumber used for the top of the stand. Why would it be thought that the plywood would straighten out the top frame? It won't.

Shims under plywood: NO. Less stable than proper repairs.

Proper fix: Plane the top rim of the stand flat and co-planer. It has a hump in it--the crook is facing up rather than down--a construction error, that no one ever discusses. The only place you use shims is UNDER the stand, to correct an out of level condition with an otherwise flat and co-planer top rim.

Alternative fix: rebuild the stand, this time making sure the "crook" faces down, and the corners are co-planer. A dip in the middle is not the issue that a hump in the middle is.

What ever you choose to do, is up to you. I just wanted you to know the correct answer, not the standard shortcut "fixes," that are not fixes just because a lot of people "are doing it."

How is using shims between the plywood and the top frame of the stand not proper? The plywood is perfectly flat. The shims are as strong as the wood frame. Building up the frame with shims serves the exact same purpose as planing it down. I see no issue at all with the shims. I used 6 shims in various locations (in the center and out) between my plywood and my stand and it is 100% even now.

[dougdstecklein]

I went to Home Depot today and bought some shims, plywood, a planar, 48" straight edge, and liquid nails. I checked the 2x4's with the straight edge and they are not the problem, the tank is not straight. Regardless, I am going to try planing the 2x4s first and then I may add the plywood with liquid nails in the gaps to level it.

[CrazyEyes]

I don't see an issue with using shims either. Why would using shims to straighten the tank on an uneven floor be any different than shimming the top of the stand? There are plenty of people using shims for that reason. If there is a difference please explain.

[JustinGr]

If you all ever looked at a "Prefab" stand, be it metal or wood, and a tank on it, you would ask why it is that we are so anal over this.

Case in point, I was shopping for a tank and stand, I took 3 stands and 3 tanks, and not one of them rested flush with the maiting surface. Each had gaps. I have several 40 Breeders on store bought metal stands and all of them have some gaps.

Sure, true is better, but let's not get all bent over 1/16th or 1/32nd gap. Also, what is true or not true without water in the tank can quickly change once filled.

Just make sure the tank is level, and shim the bottom of the stand, and not the tank to stand if not level. As for filling the gap(s), Foam has been used for 20+ years that I have been in the hobby and it comes in and out of fashion, the plywood trick has also been around for a million years.

Good luck.

[mr.maroonsalty]

I wouldn't be afraid of cutting hardwood shims and using a lot of them with glue, but it will look like crap. If I was worried I would either float the top with a leveling compound and a trim board, or set a new piece o plywood or hardwood strips with plenty of construction adhesive; I would most likely set the tank on top and weight it down while the adhesive is setting up to make sure it sets true to the tank.

[mr.maroonsalty]

Originally Posted by JustinGr

If you all ever looked at a "Prefab" stand, be it metal or wood, and a tank on it, you would ask why it is that we are so anal over this.

Case in point, I was shopping for a tank and stand, I took 3 stands and 3 tanks, and not one of them rested flush with the maiting surface. Each had gaps. I have several 40 Breeders on store bought metal stands and all of them have some gaps.

Sure, true is better, but let's not get all bent over 1/16th or 1/32nd gap. Also, what is true or not true without water in the tank can quickly change once filled.

Just make sure the tank is level, and shim the bottom of the stand, and not the tank to stand if not level. As for filling the gap(s), Foam has been used for 20+ years that I have been in the hobby and it comes in and out of fashion, the plywood trick has also been around for a million years.

Good luck.

Sooo true no tank is made to engineering standards; glass is a rather flexible liquid and not very many tanks are true and most do just fine or the board would be filled with leaking tank threads. That said there are reasons they won't warranty tanks without their own stands.

[dougdstecklein]

Update: I spent about 1.5 hours sanding and then putting the tank on, taking it off and sanding more. After about 5 of these cycles it is just about perfect. I do feel like this was a little over kill. I'm just glad to be moving on. Oh yeah, the hand planer was crap, I'll be returning that. I burned up my belt sander's motor, but I was able to get it done with my grinder.

[sleepydoc]

"engineering standards" depends on what the specs and tolerances are. Glass is flexible. and a small amount of variance is probably ok. The problem is a larger variance and larger amount of flexion puts more stress on the glass and more importantly more stress on the silicone joints. The bottom glass plate will flex downward, but the glass wall that is standing on edge will not. At all. All that stress is being put on the silicone joint. At some point this joint will fail prematurely, you just don't know when.

I challenge anyone to show specs from aquarium manufacturers showing how much of a gap is acceptable under a tank; I have yet to see such data.

Given the unknowns, the problems of a blown seal in X months and the relative ease of leveling a stand before the tank has water in it, it seems like a no-brainer to me.

But then I'm just an engineer.

Dougdstecklein - sorry for the hassle of leveling your tank, but I (obviously) think you made the right choice.

[Apocrathia]

Definitely fix the stand. I had a stand that I made when I was a kid, and I made it unlevel. I used some styrofoam per my lfs's advice. It lasted maybe a month until the weight of the tank had me shimming it to get it level.

[JustinGr]

Sleepydoc,

They won't tell you what is acceptable. It puts them at risk if you are within tolerance and it still leaks.

I have two 150's, one brand new; the other is about 10 years old. The bottom braces have such huge gaps in them. Essentially, the tank rests on the 4 corners and the short sides and hit or miss along the long runs of the brace.

This alone would put stress on the tank, yet one is doing well 10 years later. I also put a veneer on the glass of a 150 I took apart after the outside corner got chipped (darn kids). The glass thickness on the front piece varied 4 thou over the span of 6 feet, and 3 thou over 2 feet in height. The bottom varied 10 thou over the same distance.

Nothing is ever going to be true and flat. Our goal should to be minimize or eliminate the gaps as much as we can, but they will be there.

[jaybfresh]

Originally Posted by sleepydoc

I challenge anyone to show specs from aquarium manufacturers showing how much of a gap is acceptable under a tank; I have yet to see such data.

I was just told directly by Perfecto to ignore a 1/8" corner gap between their tank/stand and fill with water. They said the tank would "settle" when full. I don't like that answer.

[mr.maroonsalty]

Originally Posted by sleepydoc

"engineering standards" depends on what the specs and tolerances are. Glass is flexible. and a small amount of variance is probably ok. The problem is a larger variance and larger amount of flexion puts more stress on the glass and more importantly more stress on the silicone joints. The bottom glass plate will flex downward, but the glass wall that is standing on edge will not. At all. All that stress is being put on the silicone joint. At some point this joint will fail prematurely, you just don't know when.

I challenge anyone to show specs from aquarium manufacturers showing how much of a gap is acceptable under a tank; I have yet to see such data.

Given the unknowns, the problems of a blown seal in X months and the relative ease of leveling a stand before the tank has water in it, it seems like a no-brainer to me.

But then I'm just an engineer.

Dougdstecklein - sorry for the hassle of leveling your tank, but I (obviously) think you made the right choice.

A wee bit of History: popular aquaria came out of the toy departments. One of the first major brand of tank was Mettaframe; Mattel bought and owned it for much of its existance. I would be surprised if there is even one engineer anywhere close to a name brand shop; maybe I'm wrong on that, but i believe they are made of glasscutters and glue guns and not likely those with 18-20 plus years of education. Its not like a nose cone produstion facility for a Boeing airplane where everything is observed and designed by an RPI grad. Engineers are specialists and not very many can tell you what happens in say a 1" pipe at 50gpm, but they likely have an associate who might.

I'm glad you managed to knock the crown out of it.