[SAT]

I'm attempting to determine whether it's safe to add a juvenile Royal Gramma to my 300G tank which already has a "pair". If there are any Gramma breeders in this forum, perhaps you can advise me. Before you give a knee-jerk reaction, let me describe the situation in more detail.

I have two Grammas. The elder female I obtained in 2004 as part of a group of adults, not a harem. I didn't realize at the time that you can't have two adult males in a tank... they immediately started fighting. I did learn, however, that the females don't seem to engage in this behavior. Partly as a result of the fighting, and partly because of some other stupidity, I ended up with one female. That one is now 13 years old.

The second I obtained as a 2" juvenile mid last year, not knowing the sex. A year later, the younger is apparently adult size and there is clear pair behavior, including nest building, territorial defense (ever have a Gramma attack your hand?), and other interesting interactions. However, the newer fish still looks to me like a female, despite the behavior, except that it has not filled out with eggs.

When I had the original group of adult Grammas, it was clear to me which ones were male based on body shape. To me, the males looked sort of bulldog-shaped, in the sense that the front of the body is larger than on the females. My younger Gramma today does not have this shape. At this point I don't know if it's actually a female engaging in pseudo-pair behavior, it's just not fully mature, or if I am actually mistaken about how to sex the fish.

Is it plausible that two females would form a pair?

What I would like to do is add another juvenile. I expect the juvenile will be OK until is starts to mature, and will probably still be OK if it's a female. However, I don't want to take that chance if my current younger Gramma is actually a male.

The other fish in the tank are a 12" Atlantic blue tang, two molly miller blennies and two chalk bass. I have had problems with the Grammas bullying the chalk bass, but that situation seems stable now.

BTW, it has been theorized that a female Gramma will become a male in the absence of another male. I have also seen other experts dispute this. I as a counter example I have my elder female which is clearly still female after over 10 years alone.