I put in my 125gal tank, and plumbed it through the wall into an 80gal glass sump.
... I've got a house, with a subfloor or crawl space and knew it could handle the weight... however, wasn't expecting the tank to shudder and shake every time you walked by... or the dog ran by... or we had people over. It made me nervous every time there were numerous people in the room, up close to the acrylic. So I made a plan to brace the subfloor joists.
That plan, all changed when I was buying the material. I had the plan drawn up, and a materials list all ready to go. I was standing in HomeD... and realized I was OVER building by about 500%. My normal problem when fabricating or building, as I've never wanted anything I build to break apart or fall down. So I changed a few things and opted for a "wedge" approach rather than my all-thread and heavy nut idea (jack post) with one less 4x6 beam. I'm glad I went the way I did.
Knowing I was to put in new flooring in the room, I saw cut a hole in the floor and made access into the crawl space (otherwise, I'd have to haul all the lumber from the far side of the house... and that would have been a HUGE pita!)
Not a huge hole, but one I could get a 4x6 eight feet long into.
Once I had the cutout, I dropped in the (4) 12" concrete piers that I'd use to hold up my (2) 4x6 beams. And some tools, a baby sludge hammer...etc.etc... and myself. My Wonderful Cousin, was going to be on the DeWalt sliding compound miter.... and would pass down my needed materials.
There was only 18" of crawl space below the joists and above the dirt. Thank goodness my 1962 house was fairly clean and clear underneath. Often I stick foggers under my house to kill varmits and pests, so it was also pretty clean of spiders and a lack of webs. NICE!
Here you can see the limited working room;
It doesn't look to safe, or strong... but, trust me on these wedges... they aren't going anywhere once I screwed the beam to the strapping on the concrete block, and the beam to the joists. I didn't have the room for my jackpost idea. As I'd have welded up some all-thread and a heavy nut to be able to adjust the pressure (like a car jack). However, the wedges my cousin cut... worked GREAT!
These wedges are secure, and providing a solid mating surface;
Once I got a beam in, we tested the bounce on the floor... and the fish tank still swayed. Pretty scary... as I think it could fall over at any time during a party, or small earthquake. I noticed the tank was on two joists... centered just about perfect. Hmmm... wonder why it's so unstable?!
With that, we put the second beam in. 4' from the other beam. Both of them spanning the width of the tank stand and from my house's outside wall to interior stem wall. Pretty much dead center of the room. Beams perpendicular to joists.
Each beam is 8' long, and covers almost 8 joists. Each end joist, is a double joist or considered a sistered joist and makes up into a 4x8 beam. It's not going ANYWHERE.
The second beam is in, and the floor is much more stable as well as the tank. However, the current blocking in between the joists was either loose or not a tight fit. So I made sure to add a few blocks under the tank in between the 4 joists under and just outside the tank footprint.
With the latest blocking, and two beams... the tank doesn't shake, even when a 210lb adult jumps up and down next to it. Sure makes it easier to sleep at night!!
I make some leveling supports around my hole, and begin to close it it;
After a healthy plywood patch, it's all done;
Now, I have a solid foundation that doesn't allow my tank to shake, rattle and roll.
... all I have to do now, is re-paint the tank stand, lay my new flooring, and put on new baseboard and trim around the base of the tank (I had to repair the stand from the previous owners "water leak" problems - hence it's need for repaint, clean up and trim).
Time to sit in the hot tub!!!