as anne said, juvy bichirs have external gills, and as they grow, they are retracted and absorbed back into the body. and once the external gills are completely gone, they're gone.
juvy bichirs have the ability to regrow damaged external gills. some believe external gills growing back is a sign of very good water, but it doesn't seem to be the the only explanation, since apparently some people don't really take special care of the water, and their juvy bichir's damaged external gills grow back anyway.
and whether the gills grow back or not, and how long a particular bichir keeps its external gills aren't related to its health, at least i haven't read anything that indicates that...
juvy bichirs have the ability to regrow damaged external gills. some believe external gills growing back is a sign of very good water, but it doesn't seem to be the the only explanation, since apparently some people don't really take special care of the water, and their juvy bichir's damaged external gills grow back anyway.
and whether the gills grow back or not, and how long a particular bichir keeps its external gills aren't related to its health, at least i haven't read anything that indicates that...
