i think ur fren giv him eat too much.. in my case, i thnk it is.. hmm.. when i was young.. i got alots betta havin this problem.. got bloated.. still eatin.. later on.. not eatin, then the scale will eventually stand up.. somethin like internal bacteria disease... later went to heaven liao..

but now no more d.. try not to overfeed them.. should b ok i think..

i never cure them successfully, so cant really help u heh..