They are in a 29 gallon, I don't know how old but I have had them for about a month. I know they could take months or years to be comfortable enough to spawn (if they are a pair), but they do seem to be on the larger size of all banggai that I have seen available (I would say tip of nose to tip of tail is about 2 inches). They do spend some time side by side, just not all the time. I have never seen either fish show agression so I don't think that is a problem.
One way I have heard to sex the banggai is the length of the 2nd dorsal fin. I though both were on the short side when I got them. One also had a shorter tail fin on the bottom. After a month I have to laugh at this one. The tail fin is already fully grown back and both now have dorsal fins about a cm longer then when I got them.
One of the two seems to bump his nose back and forth against the glass in one corner of the tank. It seems like he is attacking his reflection. Don't know if he is mental or trying to protect his mate (I have my fingers crossed). lol