Hello, my24" silver aro that's about 4 years old seems to be too bouyant in the tail end. For the last two or three days his back 1/3 has been floating on the surface, and today I noticed that he's blowing air bubbles out from his gills. After this bubble blowing he seems not as bouyant. The it starts again. I have not given any new food or anything like that. Is this something to be concerned about?