Earlier in this thread (but that was a while ago in real time), Mac explained that fluid bloat is "jelly like".  Basically, gas bloat is from gas trapped in the intestines/colon.  (That's why it doesn't spread into the legs.)  It may be worse on one side of the belly than the other or it may seem fairly even.  It's "hard" in that it's not watery; it's like an air-filled ball, not a water balloon.  Fluid bloat is from fluid, which can collect in several different areas or the whole body.  It's not limited to the belly, though it may only show there.  When the frog moves or the water near the frog is rippled, you may see the frog's skin and the edema (bloat) underneath it ripple too.  (I haven't seen this often even in my ADF -- which has thinner skin, so its insides can be seen more easily if the frog is under a strong light -- so if you haven't seen that you can't rule fluid bloat out just on that basis.)  It's more like a water balloon than an air-filled ball, though with a nice sturdy ACF I'm not sure how easy it would be for you to see the difference.

Does that help at all?