What does Gawking typically weigh?

Haha.. think Howdy would have to answer that... typically between 150-300 lbs. unless of course he gawks as a family, which could push it a fair bit higher..

i imagine you could draw quite the crowd with about 400 Gal. of tank space in those 3 tanks. (which without rock/glass is already ~2 metric tonnes) add 400 lbs of LR/sand... 500lbs of glass... big numbers...

i am actually going to go with 3 x 3 by .375 inch because they dont have the .313. so I am going to go bigger vice smaller.

underneath there is 2 x 10's at a 12 foot span every 12 inches running in the same direction as the tanks.
there is also a 2 foot retaining wall at the 6 foot mark running perpendicular to the joists with 2 x 12 foot pilings under that. One of the pilings is directly under where the tanks will be sitting.
there is also 3/4 tongue and grove OSB flooring.

I should be fine with the weight I think.
I actually built it specifically for tanks to go there.
however, they were going to go in the same direction as the retaining wall, but decided to put them all against the outside wall instead.
it is alot of weight, but I think the saving grace is the 2 foot retaining wall at the halfway mark. I don't see how the 2 x 10's could really go anywhere with that there.
opinions would be greatly appreciated.

btw, as for gawking.....no comment on the weight issue...I am trying to lose a few lbs ok...lol
thanks again
Neal

My worry is that you will have the footings of this steel frame, holding up 3000lbs and hiting the floor at almost exact midspan of the 2x10s. (provided im understanding your geometry correctly). At a 12'' spacing of those joists you can, at best, hope to split that load over 2-3 of them. On top of the 2 tanks you have there already, i personally wouldn't trust it. Sphelps may be able to comment better on the numbers side (don't have any refence books on hand) but my gut says dont do it.
If you can, I would say make sure there is a support (concrete ideally, or cinderblock) directly under where your stand footing hits the floor, and join the 2x10s together to prevent any torsion. (12'' pieces placed between them)

I should note at this point that my advice is only relative to the steel structure holding the two tanks. I can't comment too much on the floor holding that much weight as there are way too many variables to consider. I assumed this was on a solid floor, you'll definitely need something above normal floor conditions to support the weight on a raised floor.

Im going to go ahead and qualify all this advice as well as i've not seen your actual flooring. I really dont need to get sued after the floor collapses and causes 20K in damage. My recommendation stands though that you seriously consider the strength of your floor before you put that kind of load on it.

Something to consider: general design parameter for living space is 40lbs/sqf. the are under this tank will be facing loading about 10 times that.

Hello all
first of all - No one worry about getting sued..i don't think I would have much of a chance of sueing someone for some free advice I got from an online forum. and even if I could, I wouldn't. So no worries there.
i do appreciate your inputs.
just to clarify about the structure of the house.
the room is 12 feet across.
beneath this is a crawl space.
the 2 x 10's are actually resting on the perpendicular 2 foot retaining wall at the 6 foot mark or halfway mark, which has the 2 - 12 inch by 12 feet deep pilings.
I am not sure if this was clear.
I don't really see how, being that it is actually resting on the retaining wall in the middle of the room, that there could be any movement at all really.
or am I right out of it?
the concrete wall is 10 inch thick reinforced by lots of rebar.
let me know what u think

You should be fine with the joists but I would worry about where the feet of the stand are. (ie. between the joists.)

aluminium doesn't rust. come in aircraft grades and is light weight easy to weld and looks nice and takes powdercoat well. just a thought.

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I don't really see how, being that it is actually resting on the retaining wall in the middle of the room, that there could be any movement at all really.
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I trust the retaining wall, what i dont trust is 2 2x10s at a 6 ft span holding up 3000lbs.

http://www.awc.org/calculators/span/...rcalcstyle.asp

at 100 psf (pounds per square foor) this calc says your max span is 10ft. you've got 4 times that....