Freshwater Butterflyfish

One species, three tiers: the African butterfly fish, Pantodon buchholzi. Everything about it points up — the mouth opens at the top of the head, and the fish spends its life in the top inch of water waiting for something to land there. That makes it a surface specialist rather than a community fish, and it wants still water, floating cover and low flow.

Two hard rules. It jumps, and a gap around a filter pipe is enough, so the lid needs to be complete rather than mostly complete. And it will not chase food down; anything that sinks is gone. Feed at the surface, and skip tankmates small enough to fit that mouth. On the non-quarantined tier the DOA window is one hour after delivery — the terms are here.