Ok, This is a somewhat long story, My bf's mother has an aquatic frog ( I don't know the species) since aprox 6 years. It was in a small tank with nothing else. no plants, no stones, nothing. Just the frog. The point is she (my bf's mother) got sick and can't take care of the frog anymore, so she gave it to us to take care for it. I've had it fro around 1-2 months already. It usually eats everyday some pellets we give it, and the occasional moth, wich it just loves.
Here's how I received it.

But I was feeling a bit sad to see it all day in that small tank with nothing to do, it just sat in the bottom for hours staring at the wall. So I decided to get it a bigger tank, with plants and stones.
Here's the new house:

The problem is that when I changed it to the new tank, it stopped eating. The girl from the store told me that she could take a few days to get used to it, but it has already been a week since I changed it, and still nothing, it doesn't look too stressed, it's not always staring at the wall as before, now it swims a lot, and then rests for a while. When I get close to the tank, it always comes to the surface (it's used to being fed directly in its mouth) but I give it the food and nothing, eit doesn't seem interested. Even the few times it actually puts the food in its mouth, it just chews it for a while and then spits it out. I haven't changed its food or anything. I even tried to give it some moths, and still nothing, it just left them floating around. I've left some food floating to see if it's eating but it doesn't seem to be doing it either.
I don't know if it's still stressed or ill, but it doesn't seem to be ill, it moves a lot, and even seems to like to play with the filter bubbles.
Also, it was used to regular water, I changed it ever week or so, but with no special treatment, now I bought some drops to de-chlorine it (is that how you say it in english?) maybe it has something to do with that too?
I really don't know what to do, I've called some pet stores, but none of them have frogs so they don't know how to take care of them.
I'm felling really bad now, I just bought its new tank because I wanted it to be happier but it seems I messed up big time and I'm very worried about it.

I hope you guys can help me with this.