Dear all, thank you for the many suggestions and most important of all, opening my eyes to the concept of "stunting". It's amazing to me how many websites and ***********s (like me) just assume that it's true, and when their fish dies accept it as "fact of life".
I've not got a much longer list of "Pleco Cuisine",
and just this morning picked up a much bigger tank =)
Most importantly, just now his tummy is looking like normal again~!!
I hope Leopard lives long enough to enjoy his new digs =D
** special thanks to Bethany again =3