Help me find a fishAnswer four questions about your tank, and skip anything you don’t know.Question 1How big is your tank?Measure the glass, not the label. A “60 litre” tank can be almost any shape, and what matters is floor space.LengthcmDepthcmor pick the nearestNano30 × 20 cm12 × 8 inStandard60 × 30 cm24 × 12 inFour-foot120 × 40 cm48 × 16 inNot bought one yetdon’t narrow on thisQuestion 2Is it heated?An unheated room-temperature tank rules out most tropical species, and opens up a small group that prefers it that way.Heated22–28 °C72–82 °FUnheatedwhatever the room isDon’t know yetdon’t narrow on thisQuestion 3What comes out of your tap?If you don’t know, your water company publishes it. Or skip it.Softunder 8 dGHHard8–15 dGHDon’t knowdon’t narrow on thisQuestion 4What are you after?This is the one that decides whether you end up with a happy fish or a hiding one.A shoalten or more of one small speciesA pairtwo, likely to breedA centrepieceone fish that owns the tankDon’t minddon’t narrow on thisShow me these →Your answers become filters you can change.