Freshwater Fish Database

About the Tank Logic Freshwater Fish Database

The Tank Logic freshwater fish database is a free, no-signup reference for aquarium hobbyists who want to make confident, evidence-based stocking decisions. Every entry is written from the perspective of a working fishroom, not a content mill: the care sheets reflect what actually happens in real tanks, with notes on temperament, adult size, water chemistry preferences, and the small compatibility quirks that seller listings tend to leave out. Whether you are stocking your first 10-gallon tank or adding a sixth species to an established community, the database is designed to give you a clear answer in under a minute.

Each species card includes the four pieces of information that matter most when you are deciding whether a fish belongs in your tank: adult size (not the misleading juvenile size quoted on retail sites), temperature range, pH and hardness preferences, and a difficulty rating from beginner through advanced. Where relevant, we also call out schooling behaviour, territory requirements, and known aggression triggers — the details that turn a "perfectly compatible on paper" list into a tank that actually stays peaceful six months in.

Use the category filters to narrow your search by tank role: nano fish for small setups, mid-size community fish for 20–55 gallon tanks, bottom dwellers for cleanup crews, large fish for specimen tanks, and invertebrates for algae control and added biodiversity. The search bar accepts common names, scientific names, and partial matches, so you do not need to remember whether a fish is listed as "bristlenose pleco" or Ancistrus — both will find the same care sheet.

Once you have a shortlist, take it to our stocking calculator to check the bioload against your filtration, or to the tank size calculator if you are still deciding what tank to buy. Together, the database and calculators are built to do the part of fishkeeping that is genuinely difficult — turning a wall of conflicting forum advice into a clear, defensible plan for your next tank.