Are aquarium mats mostly myth? - Page 2 - The Planted Tank Forum
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post #16 of 29 (permalink) Old 09-02-2020, 09:44 PM
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The purpose of a mat under a tank is to distribute pressure points from the stand. If you have a perfectly planer stand surface there is no need for a mat. To check to see if your stand is planer put a straight edge across diagonal corners while the stand is under an equivalent load of your filled aquarium plus make sure there are no bumps or high spots in the top surface of the stand. Pressure points are what cause problems and leaks in otherwise sound aquariums. Under load (the weight of the tank) the stand will conform to the contour of the floor it is on... for tanks of a significant size (and weight).

How do you put the stand under the load equivalent to the weight of your tank and check across the diagonals? I don't know which is why I always use a mat.

A mat will only make up for minor variations in the stand surface whether they be bumps or twisting of the top. The twisting forces are the hardest to identify and in my experience what cause tiny leaks to develop over time as the sides of the tank tries to tear the seams of the tank apart.

Is a mat required? No, definitely not. Is it good cheap insurance? In my experience it is!

I have had a 110G tall glass tank spring a very small leak that wasn't detected for several week and created a huge mess. The tank was on a cheap particleboard stand (I was in the process of building a new stand for it) and had no cushion to distribute pressure points between the stand and the tank. For $25 I will buy a foam camp pad for cheap insurance.

If you don't want to use a mat, don't use a mat. The chances are VERY HIGH that you will NEVER have a problem... if you shim the bottom corners of the stand so the top corners of the stand are planer.
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post #17 of 29 (permalink) Old 09-02-2020, 10:48 PM
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For a rimless glass tank, or an acrylic tank always use a mat because the weight is distributed on the bottom, for a framed tank the weight rests on the frame (hence the stands metal, or wood without a top supporting board) and a mat would be detrimental because it pushes the glass up putting stress on the seams inside the frame which can cause the glass to fracture over time. Recently got a new 75 gallon tank and the stand was not level diagonally across, so to have a new one built according to my design I had to do a lot of learning from others who had a lot more experience at designing than I did but now this stand is built solid like a tank.
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post #18 of 29 (permalink) Old 09-03-2020, 01:50 AM
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Quote:
Originally Posted by ahem View Post
A mat allows movement, it's a very small amount but more movement than a firm piece of leveled plywood. Any movement of an aquarium full of water is a stress
Yes, a mat allows movement - that's the whole point!!!

A small amount of movement redistributed stresses away from a point load.

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Originally Posted by ahem View Post
The fact is nobody has done any kind of test like setup 1000 aquariums on the same flat surfaces, one with a mat and one without and see how many mysteriously explode and try to correlate that mat efficacy.
Sounds like your tank is going to be #1 of 1000 in this experiment then! We really only learn something new when someone has a hunch and does something different. The danger of course is that your tank is fine (given that you have been very careful checking the stand etc), but that someone else reads your (hopefully!) successful result as meaning "tank mats are a myth and you don't need them ever on any tank!"

Keep us posted


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post #19 of 29 (permalink) Old 09-03-2020, 05:12 AM
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Originally Posted by ahem View Post
Just received a Clear-For-Life 50g acrylic aquarium along with a Clear-For-Life "Laguna Pine" stand. It did not come with a mat. I don't think I need a mat. The top of the stand is one big piece of flat well-finished plywood.

Reading online, the reasons for a mat seem partly myth. For example I see people claiming it will "level the aquarium", which it cannot possibly do. However out of level a stand is, that is how out of level a tank sitting on top of the stand will be, mat or not. In fact a softer mat may make an out of level tank worse by compressing more on the lower side thus making the aquarium even more out of level than the stand. The other reason sited for a mat is to "smooth out the surface". Now that could make sense if I was maybe putting this on an unfinished surface or something with exposed screw heads, nail divots, etc... which I am not. On the flip side, I imagine if putting large stones and/or heavy decor in the aquarium (which I will be), the load on the floor of the aquarium could be a little uneven. If it's on a mat, I think that could cause some local slight sagging under heavy objects versus if it is sitting on a flat hard plywood surface.

In my situation I cannot fathom a reason why I'd want to put a mat under this, it seems like it would cause more harm then good. Does it make sense to go without a mat?
Did you get it new or used? I'm only asking because if used, what did the previous owner have? If purchased new I would probably follow the manufacturers recommendations as to not void any warranty.
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post #20 of 29 (permalink) Old 09-03-2020, 05:28 AM Thread Starter
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I know that it distributes the force concentrations. But what point loads? If they come from the stand in the form of a screw jutting through or warping of wood, something like that would cause me to immediately abandon the stand. I'd move every thing to another tank, empty, and work through it with the manufacturer to get it replaced. Also side note, I notice my mat under my 20G acrylic does nothing to keep water off the 3/4" plywood underneath of it. In fact it may trap moisture between it and the wood. I keep it dry but water always drips down an aquarium at some point. So that is another thing that has concerned me with mats.

There are no point loads coming from the inside the aquarium if it sits on a rigid surface. If it is on a soft surface like a mat, then rocks and heavy ornaments become point loads against the bottom surface causing it to warp ever so slightly under their weight.

A glass aquarium is a rigid fragile box, especially a rimless. It seems to make sense to put that on a mat. An acrylic tank flexes like a stiff gel (they can jiggle, depending on thickness, like a very stiff cube of jello). My bet is that for stability, it is better to put such a thing on a solid non-flexible surface.
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post #21 of 29 (permalink) Old 09-03-2020, 06:15 AM
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Quote:
Originally Posted by ahem View Post
There are no point loads coming from the inside the aquarium if it sits on a rigid surface. If it is on a soft surface like a mat, then rocks and heavy ornaments become point loads against the bottom surface causing it to warp ever so slightly under their weight.

A glass aquarium is a rigid fragile box, especially a rimless. It seems to make sense to put that on a mat. An acrylic tank flexes like a stiff gel (they can jiggle, depending on thickness, like a very stiff cube of jello). My bet is that for stability, it is better to put such a thing on a solid non-flexible surface.

I'm reading this with some chagrin because about 2 years ago I posted a similar concern here and got involved in a friendly debate about my concerns regarding support for a 65 gallon framed glass tank I'd picked up from the dreaded Craigs' List. You can read it here:
https://www.plantedtank.net/forums/9...s-support.html

In retrospect I believe the failure was due to a slightly less-than-flat surface. I'm proud of my solution and it's held up very well since.

I'm going to take exception with your statement that since it's placed on a completely flat surface that there are no point loads. I have a strong background in structural engineering and I can promise you you're mistaken. A point load is applied and the same whether there's adequate support for it or not. Place a pointed rock on your sidewalk and there's a point load. Depending on the size of the rock there'll probably be enough concrete to support it but that doesn't take away from there being a point load. My concern at the time was for the load of ~550 lbs. of water and substrate on a sheet of tempered glass only supported around it's perimeter. I was assured it would be fine but then I got thinking that we're not talking about just a distributed load but with the field stones I planned on adding there would indeed be point loads.

Anyway, that's one concern. The other is that the tank sit perfectly perpendicular to gravity on a perfectly level, flat surface, checked while under load, to avoid any torsional (twisting) forces on the tank and seams, and this is where a good mat can come in handy as it will provide some forgiveness for the inevitable, and hopefully subtle, imperfections in the platform's level and flatness. And once loaded and compressed, I don't believe there will be any significant movement. I get what you're saying about the characteristics of a glass versus acrylic tank wrt stiffness but a mat's going to be so compressed it'll be a non-issue.

Last edited by ChuckM; 09-03-2020 at 06:23 AM. Reason: can't seem to get my weaight of water correct!
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post #22 of 29 (permalink) Old 09-03-2020, 11:26 AM
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Quote:
Originally Posted by ahem View Post
My bet is that for stability, it is better to put such a thing on a solid non-flexible surface.
Seems you've given this quite some thought and listened to the pro-mat arguments (including those from two engineers, and everyone of course knows that an engineer is never wrong! ).

So guess it's time to go for it and see what happens!

Hope you prove us wrong (but if you do, please note earlier point about engineers never being wrong!)


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post #23 of 29 (permalink) Old 09-03-2020, 02:30 PM
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If the cost of a simple mat is causing you to question its use. Then perhaps this hobby is not for you.
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post #24 of 29 (permalink) Old 09-03-2020, 04:21 PM
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"A glass aquarium is a rigid fragile box, especially a rimless. It seems to make sense to put that on a mat. An acrylic tank flexes like a stiff gel (they can jiggle, depending on thickness, like a very stiff cube of jello). My bet is that for stability, it is better to put such a thing on a solid non-flexible surface."

I think you're right, the exception being any twisting of the furniture that may occur once a water load is placed on it. That's something I worried about with my 75 g rimmed tank on a 1 75" solid black walnut top. Ultimately I leveled it and placed the plastic rim right on the top. Once partly filled for water testing I placed a level on both ends and sides and saw no flex.
I could see a mat under a rimless helping relieve corner stress ever so slightly if a twist developed in the furniture, maybe helping 1/32". By the same token I could also see it allowing a tiny flex if rocks were loaded in one area.
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post #25 of 29 (permalink) Old 09-03-2020, 05:00 PM
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Quote:
Originally Posted by en7jos View Post
Seems you've given this quite some thought and listened to the pro-mat arguments (including those from two engineers, and everyone of course knows that an engineer is never wrong! ).

Hey now, I resemble that comment!
I'm not, nor ever was, an engineer. But having been through several college-level structural, statics and strength of materials courses (and done fairly well), I think I have a trained eye for these kinds of things. Like a mechanical sense. And the only way I really got to this point was learning from lots of errors. And I believe the only possible way aquariums can hold together is some kind of mysterious voodoo magic.
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post #26 of 29 (permalink) Old 09-04-2020, 05:20 AM Thread Starter
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These are all very good thoughtful points but I remain unconvinced that a mat is a good thing for an acrylic aquarium. What I proved is that we can conjecture at least as many possible disadvantages associated with a mat under an acrylic aquarium as we can conjecture possible advantages we'd get. If going without a mat represented a risk, or if just having it was "extra insurance" the manufacturer that sold me this $1400 setup would have insisted that I use one. But they recommend against the mat.

It was very good to think through this, I appreciate all the comments. If it does mysteriously and suddenly explode on me, I will post back that the other engineers were correct and this engineer was wrong.
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post #27 of 29 (permalink) Old 09-04-2020, 07:38 AM
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Good luck!


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post #28 of 29 (permalink) Old 09-04-2020, 09:18 PM
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According to Envision Acrylics, who custom made my tank, and has constructed a lot of acrylic displays for museums and casinos:

“Neoprene or low durometer buna is the only thing to put under an acrylic tank. Styrofoam is useless.”

I get the question about the bottom bowing out due to a heavy rock though and I am not sure about that one. Clear for Life uses very thin acrylic for their tanks so some bowing is bound to occur.

Aside from not knowing that, I’d rather take my chances with foam rather than not. All that said I think their biggest use is for rimless glass aquariums.
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post #29 of 29 (permalink) Old 09-04-2020, 10:26 PM
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I think that using a mat is a bit like purchasing insurance. You probably will not need it until you do and then it will be too late.

They are so cheap why would you not do it? Common wisdom is that they are far more likely to help than hurt. If it helps you will never be able to prove that it did. If it hurts you will never be able to prove that it did.

Lets not feed this any longer...
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