Flatworms can grow from a single cell :(

[Leonard]

Shane posted this just now. It's a pretty big bummer and helps explain why flatworms are virtually impossible to totally kill off

Flatworms can completely regenerate from a single adult cell — Advanced Aquarist's Online Magazine

 

[returnofsid]

Flatworms are a natural part of our aquariums. They aren't harmful at all, if their population is controlled. Flatworms don't like flow or low nutrient environments. Keeping good flow and low nutrients, will keep their population in check. There are also other means of controlling their population, via several different species of fish.

In the 6 years that I've been in this hobby, I've dealt with Flatworms in every tank I've had. However, in the past 2 years, I haven't seen a single flatworm, in any of our 3 tanks. 2 tanks have wrasses and all tanks have great flow/low to moderate nutrients.