White bubble looking stuff sounds like a fungal infection or the deadly columnaris. Test the water parameters and make sure nothing is off there.
Do you have a latin name for your "hi fin bull sharks"? That is a common name invented by a pet shop, I can bet you money they're not sharks! I'm guessing they're either Paroon Sharks - a catfish that gets over 3ft-4ft long:
http://img.photobucket.com/albums/v204/MarcusK408/paroon.jpg
Or Chinese Hi-fin Banded Sharks:
http://www.solodvds.com/images/Myxocyprinus_asiaticus.jpg
Which are coldwater and also get a good 2ft long.
Neither of which should be in the pet trade!
Test your water, invest in a good anti-fungal or anti-bacterial medication and treat the tank. If the fish recover, return them to the store.
Do you have a latin name for your "hi fin bull sharks"? That is a common name invented by a pet shop, I can bet you money they're not sharks! I'm guessing they're either Paroon Sharks - a catfish that gets over 3ft-4ft long:
http://img.photobucket.com/albums/v204/MarcusK408/paroon.jpg
Or Chinese Hi-fin Banded Sharks:
http://www.solodvds.com/images/Myxocyprinus_asiaticus.jpg
Which are coldwater and also get a good 2ft long.
Neither of which should be in the pet trade!
Test your water, invest in a good anti-fungal or anti-bacterial medication and treat the tank. If the fish recover, return them to the store.