Arowanas

Three species, each listed non-quarantined, lightly medicated and quarantined: silver, albino silver, and jardini. These are top-water predators that spend their lives looking up, and they are sold small because they do not stay small — a silver arowana (Osteoglossum bicirrhosum) is a three-foot fish that gets there faster than most people rebuild a tank.

Buy the tank before the fish. A weighted, gap-free lid is not optional; arowanas jump hard, and a tank rim is not a ceiling. Jardini (Scleropages jardinii) tops out shorter than a silver but is the more aggressive of the two — one to a tank unless the tank is enormous. Every one of these is covered by our livestock guarantee, but no guarantee covers a fish that outgrows its room.