A bigger sterilizer is definitely more effective, but the bigger it is the hotter your tank gets. Plus, it still doesn't completely irradiate the pests. From what I understand the free swimming stage is very short. Maybe 24-48 hours, which is a very small window of opportunity. Additionally, the term "free swimming" means that they are capable of swimming freely, but don't necessarily spend the entire cycle doing just that. Some argue that they are triggered instead of randomly swimming around until they run into a host. Last but not least, the one you miss can create hundreds of offspring. It never ends... That was the gist of it anyway. Maybe they've since debunked a few more myths since I last read up on it? I hope so!