Just last night I saw an add for a
flex seal paste (looked like drywall compound). IDK if it's new, or anything about its toxicity, but it might be worth checking out.
However, IME, no sealer is 100% foolproof when it comes to wood & water, and if it's a bioactive enclosure, it's often like holding a wet sponge against the wood long-term.
The only real solution (again, IME) is to keep wood separate from wet areas. I'd remove the bottom, install a heavy stainless steel (aluminum & galvanized will eventually corrode & fail) screen (something like 2 or 4 mesh), raise the enclosure a couple of inches on stainless bolts or other waterproof feet, and place it in a plastic drain pan that will catch any runoff. Many folks use washing machine drain pans, but there are other terms when searching.
Solution for a bioactive would be slightly different.
From there, the water can be drained into a bucket, drain line, or what have you.
The most important thing is getting the water away from the wood, or you'll keep getting mold, mildew, and eventually rot, none of which is good for the enclosure or the animal.
Just my opinion & experience.