Black Swordtail Platy not eating

[Dralion]

Hello! I am a little worried about my black swordtail platy, Castor. He has not been eating all that much for the past day, and did not touch the food this morning. He is in a 2 gallon tank with a bubble filter-thing, a touch of aquarium salt, and a blue platy named Pollux. I was hoping to have gotten two males (I had a problem once with a pregnant platy), but again I guess Pollux is a girl, and I think she is pregnant. I had noticed when I forst got them that Castor (my black one) was a bit of a bully, nipping at Pollux. But Pollux never seemed to let it bother him/her too much. Now that I think Pollux is pregnant, she(?) is more of the bully now. She sometimes picks on Castor, but not often. Castor just spends his time sitting just under the layer of bubbles next to the bubbler.
I also recently added a "food hoop" in the tank. It sits on the water and keeps the flakes inside the hoop so they won't float away and stick th the edges of the tank and such. My black Castor doesn't seem as smart to figure this new contraption out as Pollux (he's kinda getting the idea), but still won't eat even when I sprinkle the flakes right over his head.
I'm really worried about my handsome little guy! Any help would be appreciated!
Dralion

 

[Dralion]

I did some more looking into this forum, and found someone who has the same problem! My platy has all the same symptoms as theirs does. Am I safe to go ahead and try the treatment recommended for an internal parasite; metronidazole? Is it available in pet stores? About how much does it cost? Where would he have gotten the parasite anyway? Is Pollux now at risk, or will the medicine protect him/her as well. And what are the odds that Pollux really is *just* fat? He/she does like to eat...

 

[myriam]

M or F?

Heya,

I can't give you any advice on your fish's illness, but I can give you a tip about figuring out their gender, so you can determine once and for all if Pollux is just a big eater or if he/she is a female!

Check out this site: http://fish.orbust.net/livebearers.html

The pictures are very helpful.

Good luck!

 

[Dralion]

Something else wrong with black swordtail...

Castor still sits under the bubbles, but he's eating a bit more now.. But this morning, I found something a little more concerning- his gonopodium fins are reddish tinged, and look kinda bloody.. there's no blood in the water as far as I can tell, just in his little fins. Can anyone help my little fishie?