Fire worms, is it dangerous?

[khalisee]

Hey everybody,

I'm now finding several "fire worms" or kind of worms in my aquarium. Do you have to do something against them? Are they bad or good for the ecosystem of aquarium? Are they reproducing fast?
Here some pics

Thanks for the help :)
Khal

 

[3mm3]

Top is a bristle worm. In my opinion its great to have. Good cleaners.
Bottom is a peanut worm. Harmless