what size tank ? and if possible try to set some post under floor where tank is distributing weight to the ground , couple 2x4's nailed together or a 4 x4 then you can drive a truck on it
well that equates to around 1500 lbs , I'd say you want to shore your floor up asap make a sort of T brace set it in middle of joist span so that the top of the T sits across ttwo joist and jam a 2 x 4 under it hard so you have to hit it pretty good with a hammer
it should push the floor up a bit but not all the inch at once little at a time . that will hold fine
If I were you I'd take all the shims out and start over, sometimes when using shims less is more. I helped a friend level his tank, when I got there his stand was looking like yours. I pulled them all out and it only needed 3
You have to look at the vertical supports to know where the stand needs to be supported.
As far as the shims you want to make sure they cannot slide. And while it may be a lot of weight you'd be surprised. As well not knowing what the construction under the skirt it is hard to say. But in a case like this I would usually make a larger support that would run front to back on the stand end and screw it together. Looks like you have used tape. And if they are plastic choose something else as it is more likely to slide.
As long as the stand is touching something all the way around you are good. There can't be any part of the stand that is floating. If all sides are resting on something then the weight will distribute evenly.
Yea I just used tape for now for the leak test and test run. See exactly what I need to do first. I'm going to drain and it and do some extra adjustments before I put sand and rock in and start to cycle it.
If you are going to empty the tank you could just make a foot front to back and attach it directly to the stand. Anything I shim over a single shingle I attach permanently. Also If that is pergo/laminate flooring I would definitely attach it to the stand permanently. Also By doing this you could finish it to match so it looks a little more pleasing
Hard to tell on my phone, but those look like composite shims. If they are not, I would suggest using them. Wood will compress.
...stupid auto correct