I have 3 fish I am pretty sure have some kind of worm - mollies - 2 out of 3 act sick, the female seems normal and dark poop but how long can mollies go without breeding? Had her since spring. had all 3 of them since spring @GaryE I also had my daughter's really bloated fish in my hex tank for several months last year. I think that fish is still alive at her house, and again I haven't seen a worm, the fish currently in that tank I don't want to risk unnecessarily. The mollies were in with my bronze corydoras, and were in with some of my julii corydoras. Right now I haven't done anything. When unsure I do nothing. Right now I have 6 tanks up. I will have 9 fairly soon, I do not want migrating illness from tank to tank. Have I considered euthanizing the mollies to resolve the issue, yes. Am I going to? No. I will treat with something and see what comes out. So maybe I just treat the mollie tank with the flubenzadole and observe, since I removed the sand, and see what comes out of these poorly fish, before I decide what to do with the rest.
Can you get some photos of the mollies?
The really bloated loach - if it was really bloated and it was worms, that would be a super heavy worm burden... and if it really was worms and it's been bloated since last year, it would have died by now, and your daughter would be losing other fish from worms too. Are you sure the loach wasn't just a chunky female? Adult loaches can get quite chunky, the females especially. What kind of loach is it?
I agree that I wouldn't rush to treat something you might not have. Personally I'd worm livebearers (especially ones from a fish store) while in QT because they do often carry worms, and I've battled camallanus before and never want to again - but you really haven't seen any evidence of worms, that I can tell.
Fish get a weird appearance with worms. I didn't notice bloating - quite the opposite. The guppies I had got skinny, listless, drooping tails, before dying. They can't live for that long once they have a heavy worm burden, since the worms keep multiplying, attaching to the digestive tract and causing internal damage, and sucking up all the nutrition and starving the fish. I've started to recognise when fish have what I think of as that "wormy look" now, but they tend to only look like that once the worm burden has really taken a toll and they're close to passing away.
I was losing fish for months before I finally saw the tell-tale red bristles sticking out of one guppy, and learned what I had. But I lost a good amount of adult fish, and young guppies passed away at about 2 months old. Not older, not younger. I figured that by two months, they'd ingested worm eggs that had hatched and grown, but the fish weren't as developed and grown as the adult fish, so couldn't handle the worm burden for as long as an adult that ingested worm eggs.
I'd QT the mollies you're worried about, perhaps worm them in the bare bottom tank to see if you find anything, but monitor the rest. Look for stringy white poop, that wormy look I described, and red bristles. But I think if you had camallanus worms, you'd know it by now because fish would be dropping like flies after a time.