AquariumStocking

What Size Tank Do Harlequin Rasboras Need?

Adult standard length 1.8 inches. Keep a group of at least 8-10 on a 24 × 12 inch base, about 14 US gallons.

Full breakdown: how many fish per gallon. Full breakdown: how many fish in a 20 gallon tank.

Quick answer: Harlequin rasboras (Trigonostigma heteromorpha) need a minimum base of 24 × 12 inches, about 14 US gallons, and a group of at least 8-10, at an adult standard length of 1.8 inches (Seriously Fish). The filter is 215-270 liters per hour (56.80-71.33 gallons per hour). Temperature is 70-82°F with a 75-100 watt heater, while Aqueon lists 50 watts for the 5-20 gallon band that contains about 14 gallons.

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The figures

FigureValueSource
Adult standard length1.8 inSeriously Fish
Minimum aquarium base24 × 12 inSeriously Fish
Approximate volume14 US gallonsSeriously Fish
Group / socialGroup of at least 8-10Seriously Fish
Filter rating215-270 liters per hourSeriously Fish
Filter rating in gallons per hour56.80-71.33 gphCalculated from the published liters per hour ÷ 3.785 (Seriously Fish; 1 US gallon = 3.785 liters)
Temperature70-82°FSeriously Fish
Heater on the profile75-100 watts, assuming a room around 68°FSeriously Fish
Aqueon band that contains about 14 gallons50 watts for 5-20 gallonsAqueon
Aqueon 100 watt band15-40 gallons (14 is below 15)Aqueon

Full breakdown: what size filter for a 20 gallon tank.

How to size it

Same floor as the cherry barb, different heater. Seriously Fish wants 24 × 12 inches, about 14 US gallons, and a group of at least 8-10. That headcount matches neon tetras, not the cherry barb's 6-10. Adult standard length is 1.8 inches, a little under the cherry barb's 2.0 inches and over the neon's 1.2 inches.

215 ÷ 3.785 = 56.80 gph. 270 ÷ 3.785 = 71.33 gph.

The filter box is the shared one: 215-270 liters per hour, ordinary four-to-five turnover on about 14 gallons (56 and 70 gallons per hour), not the ram's gentle 29.06-42.27 gph.

The profile then asks for more heat than the volume chart does. Listed temperature is 70-82°F with 75-100 watts, assuming a room around 68°F. Aqueon gives this volume the 50 watt band only, because 14 is inside 5-20 and below 15. 75 watts and 100 watts are on the species profile; they are not the Aqueon rows that contain 14 gallons. The 100 watt Aqueon row begins at 15 gallons. Both numbers stay on the page so the gap is visible.

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Accessory: a 75 watt heater, the bottom of the profile's 75-100 watt span. Aqueon's band for about 14 gallons is 50 watts. Shop a 75 watt aquarium heater on Amazon

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FAQ

What size tank do harlequin rasboras need?

Seriously Fish lists a minimum base of 24 × 12 inches, about 14 US gallons, for Trigonostigma heteromorpha, and a group of at least 8-10. Adult standard length is 1.8 inches.

What filter rating is listed for harlequin rasboras?

Seriously Fish lists 215-270 liters per hour. Dividing by 3.785 gives 56.80-71.33 gallons per hour.

What heater wattage is listed, and what does Aqueon say about 14 gallons?

Seriously Fish lists 70-82°F and a 75-100 watt heater, assuming a room around 68°F. Aqueon lists 50 watts for 5-20 gallons, which includes about 14 gallons. The 100 watt band starts at 15 gallons.

Sources