Dropsy or impaction?

[mapdoggis]

I got Mango from Petsmart a week ago and he finally ate one cricket yesterday. He's been lethargic until he ate. Today he's all over the place but his belly looks awfully round for having consumed only one 1/4" cricket. Or is that normal looking?

I just changed out half the water yesterday with boiled rain water. I have pothos growing in the water. Other plants are in their own containers. And I changed the filter 3 days ago.