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Oldhouse and fish tank


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Here is the conclusion to a great article which should answer many of your questions, but I suggest you read the entire article found here



Aquariums up to 55 gallons can be placed almost anywhere without much worry at all. Many tanks larger than 55 gallons and no more than 125 gallons will be okay, if they are placed in a good structural location and your floor framing is free from significant defects. For example, a 125 gallon tank, on a wooden stand, placed perpendicular to the joists up against a bearing wall, will often be okay without any additional structural support. If your tank is over 125 gallons, then it's likely that you should consider adding supports under your wood framed floor. Please realize that these are generalities that may or may not apply to your particular situation.

If you do decide to increase the strength of your floor, just keep in mind that this is best done before the aquarium is placed on the floor and the floor has deflected under the load. For example: Let's say that you fill that 180 gallon tank with water and then later get concerned. So you go into the basement and nail another 2 x 10 right alongside the existing 2 x 10 joist. (see: Sistering Floor Joists ) Unfortunately this doesn't accomplish much since the load was already in the existing 2 x 10 and you haven't removed any stress out of the existing 2 x 10 by adding another joist. If you had added the new 2 x 10 first, and then put the aquarium on the floor, then the joists would have deflected together and shared more of the load. Same idea with a post. You should either add the post first (before you fill the aquarium with water) and shim it very tight to the underside of the joists, or you should jack upward so that the post carries more load. (see: Jacking Up a Floor Joist not my site)

(see: Sistering Floor Joists )

And now for the most commonly perpetuated myth of all. Someone in the forum asks if they think it is possible to place a 120 gallon tank on the second floor of their apartment. The answers inevitably go something like this: "I see no reason you can't. I've had a 125 gallon aquarium in my bedroom for years."

Myth #17 : "If my floor didn't collapse with a ??? gallon aquarium, then your floor should be okay too"

Since the person posting the question provides no information at all about the composition of the floor construction, the span of the floor framing or the relative position of the tank, there is just no way for anyone to provide a logical answer. Yet answers flow from people perfectly willing to compare apples to oranges to watermelons to come up with a recommendation. (And in this example the comparison is even a worse because the 125 gallon tank is 6 ft long and the 120 gallon tank is only 4 ft long.)

If you know why the answer given in myth #17 is so illogical, then you understand why I decided to sit down and write this all out. I wanted everyone to have a very basic understanding of the many factors that go into the evaluation of the structural capacity of a floor framing system. I wanted to give people some guidance on where to best position their tank and when it is best to seek some outside guidance. And most of all, I wanted people to stop believing in and perpetuating the myths that spread through the internet like wildfire. Unfortunately, if you hear the same advice repeated over and over, you can start to believe that it is a commonly recognized fact. Hopefully, now we can get rid of the discussions about the; woman in high heels, the man in the bathtub, the people jumping off the sofa and the cure-all plywood under the tank.

Kevin Bauman

kbauman two at att dot net

(replace "a" with "@" replace "two" with "2")

Due to this article I tend to get a lot of emails asking for advice. Please understand that I can't give specific advice to anyone without incurring some liability for that advice.You know that ....."no good deed goes unpunished" in our wonderful legal system. (You wouldn't expect a doctor to provide you with a prescription based upon an internet email, would you?) This article is generic and that was by design. In any case, no one has ever supplied all the technical info I would need anyway.

1.) How far do the joists span?

2.) What type of wood is it? (Southern Pine #2, etc.)

3.) What is the size and spacing of the joists/ (2x10's @ 16" on center, etc.)

4.) Are there any notches or holes drilled in the joist for plumbing etc?)

5.) Has there been any water damage or insect damage?

6.) Are there knots or other imperfections in the joists?

7.) Where exactly is the aquarium located? (at the end or midspan of the joists?)

8.) Is the aquarium parallel or perpendicular to the joist span?

9.) Is there adequate bridging/blocking to distribute the load?

10.) Does the stand have 4 legs or a continuous runner?


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What size range were you thinking?

It's not uncommon for people to add additional structural support on pier and beam foundations to hold up larger tanks. But it really depends on the location and size of the tank and actual engineering of what you're putting it on. Some larger tanks are actually better than smaller footprint, but higher volume tanks because they spread the weight out more. Something like a tall 200 gallon cube would be much worse than a longer shallower tank. Also, depends on whether the stand uses legs or if the entire base is against the floor.

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My vote is make is huge, large enough that if it breaks through the floor you can turn it into an indoor pool, OR better yet a profit center: keep it as a salt water/reef, and charge for scuba lesson/excursions, marine education,

marine exploration, etc...

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