Male Deltas, Doubletails, Veiltails, and Halfmoons all have long tails. Females ALL have short tails. Male Plakats are the only males with short tails. You can distinguish them as males by the sharply pointed anal fin, and by their "beard." When the fish in question is flaring, an extra flap of skin (for lack of a better word) will extend from the gills. The difference is marked, and this is not present in females.
Here's a picture of one of my young male Deltas. Notice the long fins. Also, note the "beard" as I explained. That extra flap of skin within his gills when he flares? That very clearly marks him as a male.
Here's a picture of one of my females. Notice the lack of a defined point in the anal fin? I'm sure she's a Veiltail.
Here's a picture of one of my male Doubletails. His fins are good and long, so it's fairly obvious he's a male.
Here's a picture of one of my male Deltas. His fins are also good and long. Another definite male.
It can be hard to tell on some fish what gender they are. Havoc here is pretty little, fairly young, and doesn't have his fins fully grown in yet. He is a male Plakat. If you look closely enough at his anal fin, you can see that it is much more pointed than my female's anal fin.
Does this help any?
