Color changing Goby's???

Ok, so I am wonder what is wrong with my tank, i have this goby picture below, hes very very active but the other day i was watching the tank and I seen him(I only have one like him) and he was a dark grey with white spots, today i see him and his back to his normal looking self. I had an algea benny but I thought the crab got him, as I haven't seen him in months...so why is this goby changing color?? do they do that??

Now to make this even stranger I bought 2 neon goby's at the lfs, after a few days they began to make tunnels under the rock work, then i notice they changed from having a blue strip to having a black body with white spots. They are so long that they look like eels, but they have that goby face. So whats up with that? why are things evolving in my tank? Just think this is really interesting and strange. yes i'm workin on the algea problem ;D


the neon

 

Sure that's a neon? Looks more like an engineer goby.

 

yep I think your right, they are engineering goby's, another thing the lfs sold that was suppose to be something different, though they did look like neons when i first got them. They are still cool, when the don't steal the shrimp pellets from the crab, its funny to watch.

 

How big is your tank. They get pretty big, and can be quite destructive to your rock work.

 

I second or 3rd the engineer gobie

 

Its over a 30gal probably closer to 40. I haven't had any problems with them, they've been in about 3-4 months. I don't have huge amounts of rock work in the tank so they don't bother things to much, they are forever barring the hermits though.

 

as for the first guy changing color, mine does it all the time depending actually what rock he's on, i think it's some kind of comoflagueing (sp?)

nothing to worry about!

 

I hate when the LFS store sells engineer goby's as neon gobies - every time I see that I say something just to break balls.

Cool fish otherwise if you have the room and don't mind the mess