Betta varieties, 15 of them.

Every fish here is the same species, Betta splendens. What the variety names describe is either fin shape (veiltail, halfmoon, plakat, doubletail), color and scale genetics (koi, marble, mustard gas, dragon scale, black orchid, butterfly), or size (giant). Care is broadly identical across all of them: a heated, lidded, filtered tank of 19 liters (5 gallons) or more - the Giant is the one exception, needing 38 liters (10 gallons) - one male per tank. The list suits anyone deciding what to buy and wanting the genetics stated plainly rather than the shop label. The trade-off runs straight through the group - the heavier the finnage, the worse the fish swims and the more often fins tear or blow out. Rosetails are the clearest example; short-finned plakats are the easiest keep. For the species itself, start with the betta basics guide.