Baby Mollies sudden balance problem

Question
Our fry are 2 weeks old this friday.  A few days ago (maybe 5 or 6 days) one of our 17 started swimming in corkscrews and that one and 2 others sleep on their sides on the bottom.  Up until I noticed the problem, they seemed fine except that 2 of them ate at a right angle to the surface of the water instead of at a 45 degree angle like the others do.  The 3rd one was born with a problem in that he has never been able to really get off the bottom.  I figured he would just die because he couldn't get to the top to eat, but I guess he finds enough to eat that sinks because he seems to be doing fine except that he is quite a bit smaller than the others.  

Have you ever heard of fish losing thier ability to "right" themselves in the water?  Is it a birth defect? Some problem with the water?  Some physical damage done sometime after birth?  By the way, they have been living in a fry cage made out of netting hanging in the same aquarium as our adults.

Thanks for your help (sorry this is so winded!)
Bridget

Answer
Hi Bridget;

Poor little fellas! I would suspect a swim bladder problem. It could very well be genetic. The swim bladder is an organ just below the spine that controls buoyancy. Here is a good article about swim bladder troubles and their causes;

http://www.fishtanksandponds.info/care-maintenance/health/swimbladder.htm

At Your Service;
Chris Robbins