What should I seal this with?

[GpBp]

Hello! Last week I made a food/water dish following https://youtu.be/hHPAWLBI6yg this video. It went well! It turned out great, I used a suction cup on the back to hole it onto the back (It'll hold her, Pockets 3 grams ). Anyway, Pocket doesn't really have any nice hides, so I decided to make her one. I got a foam ball and carved out the inside. I was going to grout it as the next step, but I'm not sure what to do! I know Mod Podge has a weird reaction with Eco-Earth, so I cant use it because I want to put some Eco-Earth in the hide. And Idk if she'll smell the grout... (It doesnt give off a strong odor at all, especially when sealed). So I'm not sure! What would you do to the foam? Thanks!
(First pic is dish I made, second is foam ball. As you can see, she has a good amount of room to lay)



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[GpBp]

Forgot to mention: I textured the ball with my fingernail lol. I wanted to give it that rocky look

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