Sick Molly, please advise

[mamaber]

Okay, so I finally got the tank parameters back to normal after my vacation disaster. I restocked my tank about two weeks ago with 4 new mollies, to bring the total count to 6 mollies in a 30 gal tank. Those are the only fish in there. Well, one of the remaining two has developed little black spots all over his body. They look like flecks of pepper. I've looked all over the place and can't figure out what it is. I assumed it was a parasite, so I treated for parasites for a week. He developed more spots. Otherwise, he's been acting perfectly normal until last night. I found him laying on the bottom of the tank. Still breathing, and moving only when another fish came to bother him. I thought he'd be dead by morning. This morn, he greeted me at the top of the tank at feeding time. After eating, he went back to the bottom of the tank. Every time I go look at him, he swims to the top until he realizes I'm not feeding him, then goes right back. None of the other fish have developed the spots and are all acting normal. Tank parameters are normal, NitrItes at 0 and NitrAtes about 5. Temp is steady about 80. There is a little salt in the water as well. All other fish appear fine. Thoughts? Advice?

~Amber
ps. how many mollies could I safely put in this 30 gal tank?

[Sable]

Did you quarantine the new mollies? If so, for how long?

I'm not sure quite what's going on; I'll research it. However, you cannot get any new fish until this issue resolves itself and you have a clean quarantine tank set up. Additionally, I believe 6 mollies in 30 gallons is just about stocked in any case.

[mamaber]

I didn't quarentine them....didn't even think about it. I'm fairly new to keeping fish. Makes sense to do so, however. I will next time. Either way, the sick fish is one of the remaining two after I got back from my vacation. (There is a previous post regarding that, if you're curious. But basically it was a case of over feeding by a fish-sitter and all but two fish died. When I left, there were 10 mollies in there.)

I don't plan on getting any new fish until this is resolved. I was just curious about how many I could put in there.

Thanks for your help.
Amber

[mamaber]

UPDATE....

He's not doing well at all. He's getting noticably thin and has stopped eating. The poor thing tries so hard to swim around but at this point, he gets about an inch off the bottom, and falls back down to the gravel. Could it be a swim bladder problem? Please, any advice would be greatly appriciated.
Thanks,
Amber