New Mollies With Digestive Problems?

[lanpie123]

I've been given 30 mollie fry by a friend to start up my tropical tank. Their tank is well established and healthy as far as I know and in my tank I previously had large goldfish to run a cycle through. All seem well adjusted after 2 weeks, foraging, growing etc however I have noticed their poop is becoming elongated and stringy, some parts are also white/clear. I did notice that my goldfish had the same issue on a few occasions. I feed sparingly with trop flake & bloodworm but occasionally drop an algae wafer in which my goldfish also used to demolish. I thought maybe constipation but after online searches i'm concerned it may be intestinal parasites or an infection. The poop isn't entirely stringy but it's alarmingly changed in nearly all of them in the last few days. I couldn't get them still enough for a photo so i've uploaded a vid to youtube which is in the link below. It's quite poor quality but if anyone can see, some advice would be extremely appreciated

https/www.youtube.com/watch?v=n8b82ADxdXQ&feature=youtube_gdata_player