Little Nudibranch..

hi yesterday when am staring at my Hammer i noticed small creatures moves slowly on it they are purple and very beautiful ..
any way ...are they good or bad ..where they came from ??

 

I am guessing flatworms, common pest on Euphyllia. Without an image hard to say, could be nudibranchs, regardless if they are on your Euphyllia they are probably eating it. That is what nudibranchs do, very specialized eaters.

 

They hitch hiked in on some coral or live rock you added. Generally they are bad for some coral. They may be feeding on your hammer. I wold remove them as they will most likely die off when they eat all of the food that they feed off of. Siphon them out is the easiest way.

 

omg...when i google it i found its name urple Nudibranch
so how to siphon it ~? :S

 

Get some airline or plastic line slightly larger, start water flowing through the line into a bucket and then put the end right next to the little beasts and remove them.

 

thanx 2In10 i'll try it tonight
but i really loved them their shape & color

 

You could make a pest tank, or keep it in the sump/refugium.