Should they stay or should they go?

These guys look like trouble although I haven't detected any problems yet.

First one is a crab
Second one is a large worm.

So my question is, what the hell are they doing in my tank and should I get rid of them.

These are shoot from the hip videos so not the best shots but I had to be quick.

 

1st looks like an emerald crab and the second looks like a large bristle worm. Most people never have problems with either one, but have heard a story or two about how "my emerald crab ate this" or I had a bristleworm that did that".

IMO- they are harmless and help keep your tank clean. The emerald will eat mostly algae and are actually purchased as a solution for bubble algae- looks like you got a free one!

 

crab - its a agles eating crab good guy, cant think of the name right now

worm - look like a fire worm, mixed views on that one. all i can say is dont touch it with you hands.

 

Ok, thanks guys. I see things like this in the tank and first thing I can think of is to get them out if I didn't put it there.

Glad I asked.

 

with crabs...i just don't keep em in main tank anymore they are refugees to the refugium.
i've had to may rogue "safe" crabs..... a good rule of thumb with crabs is if the have very sharp pointy claws they are not great in reef.....that guy has blunted tips on pinchers ...he looks ok
small bristle worms i don't mind....i read somewhere bigger ones can be rock drillers...so i just remove them

 

The crab is a 'Black Mithrax crab' a friendly cousin to the emerald mithrax crab. They are reef safe, but will eat hermits for fun. When they molt Hermits try and eat them.

The worm looks like the dreaded eunice worm (very bad fireworm) that can grow to over 2 feet. GIT RID OF IT AT ALL COST!

 

Yeah, get rid of the worm. No big worm can be good for your tank. It will just cause trouble.

 

Black Mithrax crabs are great...had one that came in as a HH for several years in a mixed softy/LPS reef.

That worm is NOT a Eunicid, which are not fireworms, but are still bad juju (they are very predatory and should be removed). It does appear to be some type of bristleworm or fireworm, but we'd need some clear and better lit shots to try ID-ing it. That being said it's most likely a Eurythoe sp. of bristleworm, as it doesn't appear to have the "bristles" arranged in tufts like Hermodice sp. fireworms.

I wouldn't worry too much about the worm unless you simply want to remove it.