Hello, ya'll, I was paged over here
The #1 question I get PM'd is "why is my watchman goby turning grey?!" Sometimes it's because the fish was pale when the lights first came on in the morning (normal), but that's not the case this time.
Truthfully, no one knows why some are grey and some are yellow, but it is a reasonably common occurance and is nothing to worry about. I do have some theories. There are a couple of things to know first:
There is some indication that when the species was originally identified, it was a grey specimen. Clearly, collectors looking for "yellow" watchman gobies are going to be looking for yellow fish, which is why we don't see grey ones in the fish stores. (Or the grey ones get mis-labelled.)
The dark bands across the body are there even on yellow fish, they are just not as obvious. When the yellow starts going away, they appear more pronounced. Also, YWG's have some camoflauging ability.
Finally, MOST breeding pairs have one yellow male and one grey female fish, like my avatar. But, this is not set in stone, some breeding pairs are both yellow and some are both grey -- like mine are now, since my male has also turned grey.
Here comes the theory part -- I suspect that YWG's can change sex, and the grey coloration is usually a female fish They yellow coloration signifies a male or a sexually immature fish. Their ability to camoflauge may be what accounts for the "matched" pairs. My grey male, for example, is in a tank that is almost all grey:
To complicate matters, Amy Drehmel (who commercially breeds them) has reported batches of very small juveniles with BOTH yellow and grey members, all of which turn yellow when they go to new homes.
The bright blue fins go with the grey color variation and can get very intense. There may be some environmental factor that triggers the color and/or sex change that we just don't understand. They may not even be linked, but the evidence leans in that direction.
My female used to look like this (the small on on the right), the night they were paired:
Two weeks into pairing, showing her color change:
Four weeks into pairing, when she was pregnant with their first spawn:
How she looks today:
Anyway, dugg, don't worry. I think there is a good chance that you need to start referring to her as "she," but I can't say that for sure.