The short answer
A 55 gallon (roughly 200 litre) tank is a large, forgiving community aquarium. You can keep several shoals plus a centrepiece species — think 24+ small schooling fish across two or three species, a bottom-dwelling group, and a standout centrepiece. But numbers alone mislead: stock by each fish’s adult size, bioload, schooling needs and temperament, backed by filtration that can process the waste.
What sets the real limit
The ceiling on any tank is how much waste your biological filtration can convert and how stable you keep the water. A large tank buffers parameter swings, so a 55 gallon is far more relaxed than a nano — but it is not limitless. Messy or large fish (big cichlids, plecos) eat the budget fast, while a school of nano fish barely dents it. Match the filter to the tank and keep nitrates low with regular water changes.
Sensible 55 gallon stocking ideas
- A classic community: a group of 5+ angelfish over shoals of rummynose tetras and a corydoras group
- A livebearer showpiece: mixed mollies, platies and guppies with 2–3 females per male, plus otocinclus
- A rainbowfish display: a shoal of Boesemani rainbowfish with a peaceful centrepiece
Schooling species always need 6 or more of their kind, and avoid combining fish with very different temperaments or water needs.
Before you stock
Cycle first — see how to cycle an aquarium. Size your filter through the aquarium filters hub, plan the mix using how many fish you can keep, and see the best large aquariums if you’re still choosing the tank. For the design method, read how to plan a community tank.