Starving Mollies?

[kojote]

over the course of a few months, i've noticed my mollies slowly getting thinner and thinner. i had bought them while they were pregnant and assumed that non-pregnant female mollies naturally looked this way, and wasn't too concerned, until i noticed them continuing to become thinner. i always monitor my fish when i feed them to make sure everyone is eating and behaving normally and they all always got their share of food, so i was stumped as to why this was happening. last night i noticed the smaller of my mollies had shrunk to skin and bones and was highly alarmed, and planned to move her to my quarantine tank in the morning but when i woke up today she was dead. i moved the remaining molly into the quarantine tank and dropped some flakes in there to see if she'd eat (she did, and still is currently). so what's up? is this some kind of parasite? i'm to understand that mollies like some salt in their water, is this a side effect of not adding salt? if i did add salt, would it harm any of my other fish and what type of salt should i add? any advice is welcome.
my tank is 20 gallons, long, inhabited by 2 mystery snails, 5 cherry barbs, 5 painted platys, and 5 mollies 

 

[StevenF]

I would recommend changing the food.  From what I have read (I don't have Mollies) the food should have a far amount of plant mater although they have been know to eat  live small animal or dried bloodworms worms.So the first thing I would do is feed them more often and increase the veriety of foods you feed them.  
 
I don't have any advice on parasites or salt.    You might want to discard your old food.  Maybe is is contaminated or spoiled and making your fish sick.

 

[kojote]

since posting this my male molly has also started acting strange; he appeared dead but moved and flared his dorsal fin when i tried to net him, he's now in with the female molly (who had started to hang out on the bottom of the tank) in the hospital tank, they're both sitting on the bottom and not moving and have been that way for hours. they're alive, just not swimming, sitting right next to each other in a cave i have in there. i'm at a loss and i'm pretty distressed, this only seems to be affecting the silver mollies i have had for awhile now. i recently added 3 mollies and the 5 cherry barbs nearly two weeks ago, but they were healthy and my platies are fine. it's just these three mollies that this is happening to, i'm not quite sure what this means or what to do.
 
thank you for your advice, StevenF. i appreciate the reply and i'll take that into consideration.

 

[RobRocksFishTank]

What are your water parameters? It is very important to establish that the environment is okay before making any suggestions.

 

[Baccus]

We really want to help you and your fish and the best way is to get as much information as possible from you about your set up.
Things such as
How long has the tank been established?
What regular tank maintenance do you do? Eg Weekly 25% water changes with conditioner to remove chlorine and chloramines
What temperature is the tank?
Where the new fish quarantined prior to being added to the tank with the other fish?
Do the fish have live plants in the tank with them?
Any other fish symptoms? Eg long stringy clear poo
laboured breathing ? Eg fast/ rapid gill movement
 
To me it sounds as though the fish may have an internal parasite possibly worms.