Bettas & guppies, variety by variety.
The two most-sold aquarium fish are really catalogs of lines with opposite trade-offs - a plakat betta is nearly bulletproof while a rosetail can barely swim, and guppy strains range from hardy old cobras to inbred show lines that need pampering. Here are 21 profiles with the honest genetics attached. New to bettas entirely? Start with the betta basics guide. For the species itself, see the guppy basics guide.
🐟 Betta varieties One species, wildly different fins - from bulletproof plakats to fragile rosetails.
🌈 Guppy strains Pattern and tail-shape lines of the world's favorite livebearer - plus the wild-type Endler.
The more extreme the finnage or the purer the line, the weaker the fish - rosetails and dumbo ears pay for their looks in torn fins and swimming effort, and heavily inbred show guppies live half as long as scrappy mutts. If you want easy, pick the variety closest to the wild shape: plakat bettas and common-strain guppies.