Aquarium Calculator

Multiply length × width × depth (in cm) and divide by 1000 to get the volume in litres.

The general rule is 1 cm of fish body length per litre of water. For an average 5 cm fish, that is one fish per 5 litres. This is a guideline — species and filtration matter too.

One litre of water weighs 1 kg. A 128-litre tank holds 128 kg of water. Add the weight of the stand, gravel, and equipment — the total can exceed 200 kg.

Always use the internal (inside) dimensions. If you only have external measurements, subtract the glass thickness — typically 8–12 mm per side.

Goldfish need at least 60 litres. They produce a lot of waste, so efficient filtration is essential.

Your filter should turn over the tank volume 4–6 times per hour. For a 100 l tank, choose a filter rated at least 400–600 l/h.

Change 20–30% of the water every week to maintain good water chemistry and keep your fish healthy.

Neon tetras, danios, guppies, and rasboras work well in tanks up to 50 l. Avoid territorial or large species that need more space.

For a 5 cm substrate layer, you need about 1.5–2 kg of gravel per 10 cm² of floor area. An 80×40 cm tank needs roughly 5–7 kg.

Tropical fish need 24–28°C; coldwater fish like goldfish prefer 18–22°C. Use a heater with a thermostat and monitor temperature regularly.