How Much Weight Can A Fish Tank Bottom Hold Safley?

[plecostomus-mad]

ok, sounds reasonable chris. so how can you tell if its tempered glass? mine looks green from the side of the glass?i have supported the bottom with Styrofoam.

 

[karin]

Take a look at this: http/www.youtube.com/watch?v=PgEwEiTyYcs

Great video. I was stressing with my new tank, every new rock a little sand came out... no more! Cool

 

[chrisbassist]

tempered glass usually has a stamp or mark indicating it as such (in fact it's a legal requirement most places)

but really, how many rocks are you adding? you SHOULDN'T really have to worry too much...

andhopefully if theres someone here who hasput that many in their tank before they should be able to help...

ok, that 10G in the vid,

it was holding 220lbs... EASILY.

now divide that by 7 (safe margin of error since a lot of tempered glass is 4or 5 times stronger) gets you 31 lbs... now assuming we're talking US gallons, thats 8.5 lbs (approx) in water, leaving over 22 lbs left for rocks, and if that's the standard strength required for a tank, then I'm pretty sure that you're not gonna overload it with a few rocks. since the glass can take 200% MORE than what the water weighs. add that to the displacement of water, and suddenly a few rocks seems pretty harmless.

building in a larger error margin, I'd say unless you're coming close to DOUBLING the weight of the tank, you'll be fairly OK.

EDIT: you might also think about the fact that no doubt your tank will be better supported underneath, being supported from at least the 4 edges, rather than the 2 in the vid...


EDIT:
is iot the tank in your sig? the pic? since thats being supported along the entire bottom, nd therefore, the wood underneath should help taking a load as well... It's surprising how much weight these things can take, I'm surprising myself with this...

 

[kaivalagi]

+1 Chris

Good call on the tempered versus normal tank glass - I didn't notice, but it does demonstrate the general principle that a standard tank will also hold more than you'd think, like you've said

 

[chrisbassist]

I didn't notice at first either.

but from the math it seems like water capacity alone on a 10 gallon tank is only a third of the weight it could potentially take.

plus the fact we don't know how much more that tank in the vid could have taken, it wasn't tested to destruction.

 

[kaivalagi]

if your tank is a manufactured tank and not hand built, these things are taken into account. It should be fine.

is there a difference? mine is glass and silicone, so im guessing its hand made, if i look close i can just make out clamp marks on the sides of the tank on the silicone.

if it was handmade, i doubt its been as rigorously tested as a manufactured.

I would think the other way round to be honest, manufactured tanks are created in BIG volumes, and the QA testing would have been done on a small percentage of those volumes. Granted that because of automation the tanks SHOULD all be the same, but there is still a risk associated and therefore a requirement to water test a tank before you use it proper anyway.

I still think a custom made tank done by a reputable firm will be safer than a manufactured brand name, from my perspective custom tanks can a lot of the time use thicker glass, have more re-enforcement at the base and be generally overkill on safety. Using 10% less silicon for example isn't really a concern for a custom tank builder but is for mass production.

I would sooner have a Seabray versuses my current Fluval for example...and the prices are quite competitive considering the customisation available to the end customer with a Seabray, especially at 55G and up.

Just my 2p

 

[chrisbassist]

although true to a certain extent,

when you make a one off tank, you have to rely on your knowledge of glass strength etc. whereas the mass produced ones, they can take some off the line,and test them completely to destruction. to see EXACTLY where the break point is for heavy loads, and impacts (since they will be different) and since glass stregth varys from piece to piece, on a one off you have no idea if it's a strong bit of glass or a relatively weak one.

either way though, you can be sure that most tank makers will expect people to load their tanks with rocks, plants etc,increasing weight load, and any that want to stay in business will still base calculations on the weakest glass they are likely to be using

 

[plecostomus-mad]

my 2ft tank was factory made, brought it home and it leaked after 2 weeks!

Chris- yes the tank in my sig is the one im putting rocks in. im not going to go overboard with putting rocks in the tank.

i thought about 35 kg of welsh slate( 60kg i ''borrowed'' from wales ) mainly for caves either side of the tank.im thinking of cutting the bottom edge of the slate that sits on the glass or egg crate so its completely flat,i have a stone cutting disc on my huge grinder then silicone it to the glass or egg crate.in fact if i was extra clever, i could cut the slate to a width of 8mm and use it as a wall too hmm....

 

[chrisbassist]

since it IS the one in your sig, not only is it well supported along the entire base, but also 50 gallons weighs in at about 420 lbs, and the rocks at 78 you could add them together to get close to 500 lbs, but it won't be that much more because of water displacement.

I'm not gonna go and look at mass info on specific rocks, but when they have a tank designed for 420 lbs, the 470/480 lbs shouldn't be an issue ina well supported tank.

since they design with these things in mind, and the stregth of that 10G seems to show us something, I wouldn't be surprised if it could hold 800 lbs or more.

and with that other tank, you may have been very unlucky, and got a badly made one which unfortunately used weaker glass... theres no way of getting things 100% every time