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Tank Size Calculator
Enter your tank dimensions or pick a common size to calculate volume, stocking levels, and filtration needs.
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Or Enter Custom Dimensions (inches)
Frequently Asked Questions
What size aquarium is best for beginners?
A 20-gallon long tank is widely considered the best beginner size. It is large enough to maintain stable water parameters but small enough to be affordable and manageable. Contrary to what many expect, smaller tanks like 5 or 10 gallons are actually harder to maintain because water chemistry fluctuates more quickly.
How many fish can I put in my aquarium?
The old rule of one inch of fish per gallon is outdated and unreliable. A better guideline is to stock conservatively based on your filtration capacity, fish species, and bioload. For tropical community tanks, aim for about 1 inch of slender-bodied fish per 2 gallons of actual water volume. Always research specific species requirements.
What is a nano tank and what fish can go in one?
A nano tank is typically under 10 gallons. Suitable inhabitants include shrimp (Cherry, Amano), snails, small schooling fish (Ember Tetras, Chili Rasboras), or a single Betta. Nano tanks require more frequent maintenance but can create stunning desktop aquascapes.
What happens if I overstock my aquarium?
Overstocking leads to poor water quality, increased ammonia and nitrate levels, stressed fish, higher disease risk, and potentially fatal oxygen depletion. Fish may become aggressive due to overcrowding. Your filtration system cannot keep up, and you will need more frequent water changes.
How much filtration do I need for my tank?
Your filter should turn over the entire tank volume 4-6 times per hour for freshwater and 6-10 times for saltwater. For a 50-gallon freshwater tank, you need a filter rated for 200-300 GPH. Planted tanks can get by with less turnover (3-4x), while heavily stocked tanks need more.