Cat Food Calculator
Calculate how much food your cat needs per day. Enter weight, lifestyle and food calorie density — get RER, MER and grams of dry or wet food plus pouch count. Free, no signup required.
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Aquarium Calculator
The aquarium calculator helps you quickly determine the volume of your tank in litres based on its dimensions. You will also find out how much the water weighs and how many fish you can safely keep, following the rule of 1 cm of fish per litre of water.
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How to use the calculator?
Enter the length, width, and depth of your aquarium in centimetres. The calculator will instantly compute the tank volume in litres, the water mass, and the maximum recommended number of fish. Always use the internal dimensions of the tank.
Calculation example
An aquarium measuring 80 × 40 × 40 cm: volume = 80 × 40 × 40 / 1000 = 128 litres. Water weight: 128 kg. Recommended fish count (average fish 5 cm): floor(128 / 5) = 25 fish.
Frequently asked questions
How do I calculate aquarium volume?
Multiply length × width × depth (in cm) and divide by 1000 to get the volume in litres.
How many fish can I keep in my aquarium?
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.
How much does the water in an aquarium weigh?
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.
Should I use external or internal dimensions?
Always use the internal (inside) dimensions. If you only have external measurements, subtract the glass thickness — typically 8–12 mm per side.
What is the minimum tank size for a goldfish?
Goldfish need at least 60 litres. They produce a lot of waste, so efficient filtration is essential.
How do I choose the right filter?
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.
How often should I change the water?
Change 20–30% of the water every week to maintain good water chemistry and keep your fish healthy.
What fish are suitable for a small aquarium?
Neon tetras, danios, guppies, and rasboras work well in tanks up to 50 l. Avoid territorial or large species that need more space.
How much gravel do I need?
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.
What water temperature is ideal?
Tropical fish need 24–28°C; coldwater fish like goldfish prefer 18–22°C. Use a heater with a thermostat and monitor temperature regularly.
Results are indicative only. The recommended fish count is an estimate and depends on species, filtration, and tank maintenance. Consult a specialist before purchasing fish.
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