Urgent! Listless Platty - sick? But what?

URGENT!! I have a sweet little neon green moon/platty that in the last two days just sort of hovers and dodges the other fish who want him (I think it's a male) out of the way. He doesn't appear to be eating, and swims very little. Other than these symptoms, he appears to be fine. I'm afraid I'm going to loose the little fella. Can anyone help? I moved him last night to my small tank which is a "future nursery" where I have 2 pg platties and 1 possible pg molly (Faker is her name, but that's another story). The tank parameters are the same as his 55g home is: nitrites 0, nitrates 0, ammonia 0, ph 7.6-7.8.

Help!? I would like to save the little guy, he's my only green male for the two green females and I would like to keep the girls happy and in a family way.

Thanks in advance for any help you guys can offer.
Sharon

"Are his fins closed up and held in close to the body?" (another common symptom of illness). --- Not really, every now and then he does, but mostly he keeps them out "normally".

"How long have you had it?" --- Only since the first of September of this year. Who knows how old they are when you buy them!?

"Have there been any recent new additions or changes or other sources of sickness, or stress?" ---- I got a couple of Burmese Botias, and replanted the tank (mucking it up for about 12 hours at a time, but it cleared out well). Lost my pretty bosemani rainbow last night in the other tank - hope nothing is "going around"!

"You got any fish medications? They usually come with a disease chart and have pictures of things to look for and which medications to treat with." He shows no visual signs of any of the diseases. I only have melafix and ich treatment. Already did the melafix, and I see no signs of ich - just total lethargy! I sure hate to loose this little one...

Bump... still doing nothing but listlessly hovering - not really eating, hardly swimming, no visible signs of anything wrong. Just doing nothing at all. HELP!