Looks like you have a healthy little dude there. How long have you had him or her?
There is a place on here that you can help yourself determine what kind of firebelly it is, and if it is male or female. You might have gotten one pregnant from the store/breeder if you have only one, or it may just be eating well. Whatever you are doing, keep it up. Just make sure there is no small gravel that can be swallowed.
If you are really worried about bloat, put your newt in some dechlorinated water and see if it floats. IF it seems to not be able to get around and can NOT got anywhere but float at the top, you may have bloat. If it is struggling and swimming vigorously and clinging to the sides it probably just does not want to be in the water right now. If the little one has a pear shaped belly with the majority of the belly just ahead of the hind legs...she might be gravid..in other words, with eggs.
I KNOW there are other posts about bloat...there was one about if the chin area is involved in the bloat or not and what that may mean...and the kidneys...I just don't remember. Sorry.
From what I can see, your little guy is fine...just keep an eye on the appetite and don't allow the little one to have 50 crickets in there to gorge themselves on at a time...1 or 2 at a time is fine every couple days. No need to cause it.

If he stops eating..that's cause for concern too!
Hope this helps!