Gender differences and fin filaments in angelfish
How can I tell whether angelfish are male or female?
after all, there is only one really certain distinguishing characteristic (unless you could watch the fish while mating and thus know which one is male and which one is female): It is possible to tell the gender of mature specimens by the genital papilla; it is considerably larger in females (which of course is logic). However, it is usually necessary to take the fish out so you can see the ventral side.
One of my marbled angelfish has a fin tail "filament" like male swordtails. Does this mean anything, or is it simply another fin shape?
Provided we mean the same thing, this is just the fin shape and has nothing to do with the gender. Angelfish generally have prolonged filaments (long fin tips) at the upper and lower ends of the caudal fin. If these are missing you should check whether they were nibbled off by other fish. The filaments are not yet or not fully developed in juveniles, they will develop along with the fishes' growth.
Dr. Bodo Schnell