Royal Gramma behavior
 

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.

I've had mine turn gender in the past where I got a few small ones and the largest of the group did indeed turn male and begin to build nests for the females. I'd say you'd probably be safe to add another specimen provided that it is a smaller individual and it hasn't transitioned into a male yet. I'm by no means a gramma breeder but thought that I would share my experience. Cheers and good luck!

Thanks! So you think juveniles are gender neutral... the sex is chosen at a certain age, based on presence of a male, and is then static?