Leopold's angelfish

Leopold's angelfish is the third and least-known species of the genus, sitting alongside the common angelfish and the altum. It is often sold as the "dwarf" angelfish because its body is the shortest of the three, but that label is misleading: between its trailing dorsal and anal fins it still stands 15 to 20 cm tall, so it needs a genuinely deep tank of at least 45 to 50 cm. You can tell a true leopoldi from a common angelfish by the clear black blotch where the dorsal fin meets the body, on the fourth vertical bar, and by its rounded forehead with no notch above the eye — it is frequently mislabelled in shops. Do not buy it expecting a calm community fish: it is widely considered the most territorial and quarrelsome angelfish of the genus towards its own kind, and a breeding pair will claim a large stretch of the tank and drive everything else away. Keeping a group of five or six in a long tank spreads the aggression around rather than letting one individual bully a single victim, and tankmates should be robust species that tolerate very soft, acidic water (medium tetras, corydoras, plecos) rather than anything slow or trailing-finned. Almost every specimen in the trade is wild-caught from blackwater, which means it genuinely needs soft, acidic, warm water — around pH 6, hardness below 6 °dGH, and 27 to 29 °C — and it sulks and falls sick in hard tap water where a common angelfish would shrug it off. Peat filtration, leaf litter and alder cones help hold those conditions naturally. It is a rewarding fish, but one for an aquarist who already has soft-water and cichlid experience.