IDK about parasites, but When my tank was new (still is) I had a dino outbreak. My tank cycled for like 2 months and then after about a week after putting stuff in it and new lights I had a dino outbreak. I got the Green Killing Machine 9 watt (because it's cheap) and it completely cleared it up in like 2-3 days. I read many things of people saying it wouldn't be strong enough, but I figured what the worst that would happen? If it doesn't work in like a week or two I can just return it. Needless to say IT WORKED.