this article from cichlidforum should help:
http://www.cichlid-forum.com/articles/aquarium_weight.php
http://www.cichlid-forum.com/articles/aquarium_weight.php
How to find out if a second floor can hold a large tank?
- Thread starter Andrew1002
- Start date
Hello; An additional 200-300 pounds is the potential difference. I do not know that it will not hold just as others do not know that it will while sitting in front of computer screens. The OP posted the question, so there must be some reason for asking for opinions. I do not know of any way to find out other than having a someone with experience to take a look or set it up and see what happens.
The thought that a 125G tank will collapse any house's floor is ridiculous. If you saw all the tanks crammed in Jeff's (aclockworkorange's) dodgy little 1960's house you would understand... 
Seriously, though, I have been keeping big tanks for thirty years and have never seen or heard of a tank collapsing a floor. I have a 300 gallon (96x24x30) that sits on the second floor of our school, my 210 sits on my hardwood floor. People that tell you to consult an architect or structural engineer for a 125 gallon aquarium obviously have very little knowledge of how houses are built - a floor that won't hold up 1200 pounds spread over nine square feet most likely won't support even a single person's weight.
Seriously, though, I have been keeping big tanks for thirty years and have never seen or heard of a tank collapsing a floor. I have a 300 gallon (96x24x30) that sits on the second floor of our school, my 210 sits on my hardwood floor. People that tell you to consult an architect or structural engineer for a 125 gallon aquarium obviously have very little knowledge of how houses are built - a floor that won't hold up 1200 pounds spread over nine square feet most likely won't support even a single person's weight.
careful here. there was an MFK member on here who had a 150g tall warp and sag their floors to a noticable deflection. very bad news.
the thread might be able to be searched and brought up with the new search feature.
had a tank like this been left long term, who knows what could have happened.
so we should not be so quick to dismiss this questions as impossibilities. when you are dealing with tanks 150g and up that weigh the same as some small cars, it can potentially be an issue.
remember, tanks are in the same spot for years and years (unlike most other loads) and all of the weight is concentrated only on the contact points between the stand and the floor, not the whole square surface area of the aquarium, which many people make the mistake of assuming when doing the 'math' for these types of questions. sometimes the weight per square inch can be very very high as a result.
but I agree, generally anything up to 125 isn't bad because the tank is long and not particularly tall so the weight is not as concentrated as say a 220g, which places a lot more load on the floor and joists in the same 6 foot span.
the thread might be able to be searched and brought up with the new search feature.
had a tank like this been left long term, who knows what could have happened.
so we should not be so quick to dismiss this questions as impossibilities. when you are dealing with tanks 150g and up that weigh the same as some small cars, it can potentially be an issue.
remember, tanks are in the same spot for years and years (unlike most other loads) and all of the weight is concentrated only on the contact points between the stand and the floor, not the whole square surface area of the aquarium, which many people make the mistake of assuming when doing the 'math' for these types of questions. sometimes the weight per square inch can be very very high as a result.
but I agree, generally anything up to 125 isn't bad because the tank is long and not particularly tall so the weight is not as concentrated as say a 220g, which places a lot more load on the floor and joists in the same 6 foot span.
The thought that a 125G tank will collapse any house's floor is ridiculous. If you saw all the tanks crammed in Jeff's (aclockworkorange's) dodgy little 1960's house you would understand...
Seriously, though, I have been keeping big tanks for thirty years and have never seen or heard of a tank collapsing a floor. I have a 300 gallon (96x24x30) that sits on the second floor of our school, my 210 sits on my hardwood floor. People that tell you to consult an architect or structural engineer for a 125 gallon aquarium obviously have very little knowledge of how houses are built - a floor that won't hold up 1200 pounds spread over nine square feet most likely won't support even a single person's weight.
Hello; If the assumpton is made that an unseen house is built to some reasonable code, that the materials used were suitable for the purpose, that the builders/homeowner did the construction properly, that rot or insects have not compromised the structure or that ,as in my case, some of the floor joists had been notched, then I suppose having a knowledgable person have a look is not necessary. I have spent time correcting problems that arose from untested assumptions made by myself and others, some were quite expensive.
The person doing the checking need not be an engineer or architect, a decent contractor should have the experience to spot flaws in basic structure.
I read the article cited in a previous post, it is a good read and sheds light on the issue.
