where to begin....the first point is...I am a NOVICE cham keeper....and any thing I'm about to tell you is what I have been told here, by more experienced keepers.
And some of the things that I've learned by experience with my own chameleon.
He COULD have a respiratory infection...and being kept in an aquarium is the perfect catalyst to that.
Stagnant air and enviorment will be a breeding ground for bacteria.
Chameleons should be kept in an enclosure with at least three screen sides.
They should be misted at least two times per day, preferably three, with hot water...spraying the mist AROUND the cham, not directly AT him.
The general consenses is that they should be misted for 10 to 15 minutes each time.
But being kept in an aquarium, that wouldn't likely be possible as it would flood him out.
If his belly is what appears to be bloated, it could just be him puffing up due to stress, or if he is "sun fishing" or flattening himself out under his basking light to warm up.
Ohhh...I didn't ask that....does he have a basking area, and a UV source as well?
Does he recieve calcium supplements with his crickets?
The pale colour could simply be that he was too hot...the colours will lighten as to not absorb heat as much. When they are trying to warm up, you will notice that the colours darken.
Is the cham on the bottom of the aquarium? Or is he still holding onto his branches/plants up near the top?
For TONS of great advice...look down the forum, and you'll see lots of posts by "charm_paradise".
He has a web site, and the banner is always at the bottom of his posts.
Check out his site...it's GREAT, and filled with LOADS of info on how to properly house and care for chameleons.
He's always VERY helpful as well.
Kim
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Kim