What is the best habitat for these little ones?

[Iceni]

I can't get a good impression of the overall size of the tank from your pictures. It could either be a large tank or a small one as all the pictures are of the same corner

Looking at the setup It's damp, wet in places, Clean, and has some cover. A few hides might not go amiss, But otherwise they look happy enough.

The bark might be a concern, It's a coarse hardwood, and as such the particle size is very variable. These frogs are very very clumsy eaters and if they were mine I would not want them to eat any of that substrate. Personally our firebellys have a layer of damp coconut husk, The particles are super fine and should present no problem if eaten at all.

Don't tale my word for it tho. My opinion is simply my opinion, and I'm not qualified or massively experienced. John who is an expert with frogs has given it the thumbs up so it's probably me worrying over nothing

[John]

Thank you for calling me an expert! I actually don't consider myself an expert with fire-belly toads. However this species is tough as old boots so it's hard to go badly wrong. I think your concerns about the substrate may be valid Iceni.