Floating is a common problem with Frontosa, specially the blue species like Mpimbwe. Floating is not a desease but is caused by improper food (too much air), feeding from the surface, and stress (forced to stay on the surface and gasp air). There is even an article on how to treat floating in the Frontosa Fantasia web (now Frontosa Corner):
http://www.cichlid-forum.com/articles/frontosa_floating.php
http://www.cichlid-forum.com/articles/frontosa_floating.php