False bottom tips on large tank build?

[NeatHedgehog]

So, long story short, at some point I apparently lost my mind and I've been building a 5'x3'x4' (WxDxH) hermit crab tank out of 3/4" birch ply, which I will seal with Pond Armor. The heating controls, humidity, glass windows, doors, etc, I already have worked out.

One last potential issue I am seeing during this build is drainage. The "false bottom" method works great for smaller tanks, but does it translate well or at all to larger builds? Since we're looking at about 1,500lbs of dirt/sand/etc, how close would the bearers for eggcrate material need to be for it not to flex or snap? Or would it simply be too flimsy to the point where it would require so much support (I had been thinking 2"x4" at 4-1/2" OC) that it would add excessive weight to the final build and actually inhibit drainage?

We're "only" looking at somewhere around 1 pound-per-square-inch of weight, at most, but I am having a hard time finding anything definitive on the load-bearing capacity of eggcrate (since, y'know... it's really supposed to be a light diffuser, not a structural support).

The other solution I had thought of was to simply have a slanted piece of plywood (sealed, of course) with triangular supports under it, put down a layer of gravel on top of it, a layer of liner to keep the crabs out of the gravel, and then put the substrate on top of that. The water that reached the gravel layer would just run to the bottom of the slope and out a PVC channel. This seems like a better option, since I would be losing less height to the drainage system, it's less complicated, and pretty much structurally bulletproof. However, the rate of drainage has potential to be lower since I'm relying on a slope covered in rocks, and possibly some bacterial build up (although the water won't be stagnant, so I would think this wouldn't be too bad).

I've been through some of the other builds on the forum, but mostly they don't go into too much depth, schematic-wise, about the design of the drainage system. Just wondering if other, more experienced folks, would have some insight into the issue.

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Just to note, I am at least aware of how heavy this whole thing will be and I've taken some steps to prepare my house for it. I have already chosen the placement of the tank in an addition to the house I built myself. The tank will rest directly above three bearer beams running under the floor joists. One was an existing bearer, the other two were installed using two 20,000lb jack posts (not the cheap ones at the Home Depot, either) on top of the concrete slab which runs under the addition to help support the total load somewhere in the ballpark of 1,600 to 1,900lbs (depending on weight of tank materials). The posts for the supplemental beams are within the perimeter of the tank, so it will essentially be supported directly by the posts and slab, putting little to no strain (other than compressive force) on the joists, or on the rest of the structure.

[Orangeguy]

maby if you drill metal bars on the sides of the bottom it may support it otherwise it could possibly be to much weight.

if you send photos of it I may give you a better suggestion.

[soilentgringa]

You use pieces of PVC for supports. You can make them wider and drill the bottoms for drainage. Search false bottoms here in DIY and look at the assembly. I believe @KellyCrabbyLove had some good photos of hers.

The crabs could get stuck under the plywood and bacterial blooms kill crabs, flood or not.

IMO a false bottom isn't a necessity. Many crabbers use them, but many crabbers have also had catastrophes where they've had to dig because crabs are stubborn and can get through even the tightest of defenses sometimes.