tropical fish

[chili]

we are new to keeping tropical fish and have two questions that we can't find answers to; 1. we have an algae fish and a panda cat fish that seemed to have shrunk overnight and are really tiny now compared to their brothers and sisters bought at the same time and 2. we have a black molly fish and a silver molly fish - the silver molly hid behind the thermometer for the first week but seems okay now but the black one is lying on its side at the bottom of the tank then, trying desperately to swim to the top and corkscrews to the top of the tank, hitting anything in its way but when it reaches the top, it just floats all the way to the bottom! Can anyone help??

[B00]

I may be wrong, but im almost positive that mollies prefer brackish water, so maybe this is what is ailing the mollies at least?

Can't help with the cat fish and the other one- what's it's real name? (please don't say Trevor- lol) Maybe try Googling relevant sites and seeing if you can locate it's problem that way and hopefully some solutions?