Here it is... 20 gallon nano tank build

[RossW]

Red Eyes usually is bad
Pointed claws always bad

I have yet to hear of a non-evil hitchhiker crab.

[salvini55]

Red Eyes usually is bad
Pointed claws always bad

I have yet to hear of a non-evil hitchhiker crab.

what about acro crabs? 

[RossW]

what about acro crabs? 

You are correct!

[Vincenzo.]

typically acro crabs would be bad. but since they solely live on acro's, they are in a way 'good'. but acro crabs are still a species of xanthid crabs..

[beertech]

If you get an Acropora coral with the proper "hosting" species of Acro crab, it's a definite win win situation. The crab constantly removes any traces of algae and or damaged or dying tissue. There is usually no reason for the crab to go after living polyps. In return, it gets unlimited food supply and shelter from larger predators. Trying to identify the crab though is next to impossible. I've seen a few living in Acro colonies that have been in the store tanks for a while, and the coral is thriving. If it were a "bad" predatory crab, the coral would be stressed and have little or no polyp extension. I think observing for a while would be best, and give you time to plan it's extraction if it does turn out to be bad. 
Gord

[ordi260]

I have a picture!!!  I will upload it tonight since im at work right now!!!

The quality is not awesome because i havent had time to adjust the camera properly before he ran away...

Picture to be uploaded tonight

[ordi260]

Here is the pic of the little guy!!!  Excuse the ridiculous size...but i dont want to lose details...

[Severum]

Definitely looks like a xanthid crab to me.

[ordi260]

What do i do now???

Is my top priority is catching him???  Or it can wait for a little bit before ending up in problems...??

Ill go buy my first fishes tomorrow!

Any ideas on how to catch it   What do i do with him after i caught it???

[Rybren]

What do i do with him after i caught it???

A little garlic, a dab of butter....

[Vincenzo.]

i would catch him before i add fish.

[ordi260]

Ok whats the most efficient way to catch him???

[Vincenzo.]

look up bottle trap.
or
spear him with a sish-ka-bob skewer

[ordi260]

Ok and once trapped what can i do with him apart killing him???

[Brent Shaver]

Would the sump be a possiblity.

Thats just a guess as I dont have salt, but like you dont like killing things.

[ordi260]

I dont have a sump

[beertech]

Absolutely a predator!
I have had the misfortune of having to remove a couple of those monsters from my fully stocked reef. It was not pleasant! They feed on snails, crabs, shrimps and any fish that sleeps in the rockwork. Try to bait and trap it, then when that fails, find out what rock he's in, remove the rock and place in a container or fresh water until he scurries out. Or, in my case, the little bugger still wouldn't come out and I had to split the rock open and forcefully remove him. I forget what they are called exactly, but try googling gorilla crab or rock crab. 
Good luck, maybe someone will take him and throw him in their sump.

[JetJumper]

I will take him and put him in my sump!

[Severum]

Yours looks like the first one from the Xanthidae family.

http://www.chucksaddiction.com/hitchcrabs.html

[ordi260]

Got him!!! 

Tried to scoop him with a net but he felt the water moving each time i tried to get him so i ended up lifting the couple of rocks that he was hiding in...shook the rock very hard on top of paper towels and...poof 2 of them lol!

Now the water is cloudy because i messed around with the rock-scape...  ***lesson learned...ill never ever play with it anymore lol***  -_-

Next time ill set up traps...that was a lot of trouble but its worth it...now they are out (i hope there is no more of them in there...)

ill get fish at the store tomorrow!  

Thanks for your help everyone