Whats this worm thing in my tank ?

[bort]

Omg just saw this thing in my substrate.

Anyone know what it is ? Harmful ?

Pull one out, but the other one went deeper in the substrate.

[jayc]

Freshwater Polychaete.

There are a lot of marine and brackish-water varieties and a few freshwater ones. I'm guessing yours is a member of the family Namanereidinae, maybe one of the many species of  Namalycastis.

You're not the first to have this in the tank. Someone else here on SKF had one once upon a time. But I can't find that post now.

They feed primarily on decaying vegetation and rotting wood. But not sure if they will snack on shrimps or shrimplets.

Burn it, I say. That was also the verdict in the previous instance this was seen.

[bort]

Wish i could burn it..

Buggers are fast as.. once i probe my tweezers in the sub, they hide away. End up uprooting my plants and sub.

[Grubs]

I recently pulled down a tank and found one that looked like this.  From the size of the jaws I'd say mine was definitely predatory.

[ageofaquariums]

Most are detritivores but I have a theory many freshwater ones are root eaters similar to how many beetle larvae feed. Certainly lots of predatory marines ones, so would expect predators to be represented in fresh water too.

[Madmerv]

Looks just like something i use on a hook to catch Bream in the swan river.

Does not look like something i would want in my tank.

[uslanja]

Very nice........... we kept marine reef tanks and never removed any bristle worms that we discovered.  Not knowing exactly what this guy feeds on but being as you have seen two of them and it doesn't seem like anything unfortold is happening in your tank......... my assumption would be ditrius eaters and I would leave them be and watch for a while.  Further assuming that they are ditrius eaters you may wish to reduce their numbers a wee bit by cutting back on feeding amounts.  I think that you are lucky to have found unexpected and new life in your tank.  That is the course of action that I would follow........ for whatever it is worth.

[buck]

I've had these in one of my little rack's tanks, super hard to catch! they dig in and snap off and seeming keep living from both sides