New, chubby, fire bellied toad

[firebellygirl]

One of mine seems to like squeezing itself into the tiniest places in their tank also. I guess it makes them feel secure.

[FBTmom]

I wouldn't worry about filling in the space, unless it's dangerous. My toads love to squeeze into small spots. It's pretty funny when they squeeze in between a rock and the glass (like yours has done), but belly facing outward. You just see this flat orange and black blob through the glass.
Like firebellygirl says, it most likely makes them feel secure, and comfy.

[heyjude2200]

My FBT's love squeezing into tight spaces--when I first got them I would worry that they would get hurt or stuck, but then I came to realize that they really like to do that. I'm just very careful about the surfaces of the stones I put in there, making sure that they are completely smooth so no one gets hurt. I'm very lucky--my landlord has tons of tools and will grind & file stones if I ask him to.