thats sort of a hard question to answer. ive had full grown xanths that weighed less than 5 grams, to xanths that were over 150, i know that they sometimes attain weights over 200 g but that is rare. imo, i would consider the target range to be from about 35-140 g. females are usually heavier than males.
the male in my avatar, is now lauries zeuss, he was < 60 g but 100% healthy, little justina in my cf albums was about 125g, which was probably larger than healthy for her. fat is often confused with edema and neither are healthy but, imo, generally speaking, and all other things being equal, a lean cham would be healthier than the same cham if it were overweight, so bigger isnt always better. jmo