Aquarium Stock Calculator - Free Online Calculator Tool

Quick Answer

The Aquarium Stock Calculator is a free, no-sign-up tool that prevents overstocking by calculating safe fish numbers based on tank size, species, and filtration, avoiding poor water quality and fish stress.[1][3] Aim for 80-100% stocking capacity with no warnings for balanced, healthy tanks.[1][3][5] It's ideal for beginners and hobbyists planning community setups.

Why You Need This

Overstocking fish tanks causes overcrowding, elevated ammonia/nitrate levels, reduced oxygen, stressed fish, and high mortality—common pitfalls for hobbyists using oversimplified rules like 1 inch of fish per gallon, which ignores adult sizes and bioload, often leading to 20-50% overstocking.[1][2][6][7] For example, a 91cm/36" tank can't safely hold one adult Oscar due to its filtration strain.[6][7] Net water capacity matters too: subtract 10-15% from total volume for substrate and decor—a 60L tank yields ~54L usable space.[7][8] Beginners, community tank planners, and tropical/large tank owners (60L+) benefit most, as it factors in behavior, territorial needs, and filter capacity beyond crude metrics.[3][4][6]

How It Works

Enter precise tank dimensions (length, width, height) for accurate volume calculation, then select fish species from detailed databases using adult sizes and quantities—not juveniles.[3][7][8] Input filtration specs like media surface area and flow rate to assess bioload, oxygen use, and food input.[6][7] The tool outputs stocking levels, compatibility warnings (e.g., one male betta), and risks, gearing toward safe, beginner-friendly plans.[2][3][9]

Tips for Best Results

• Start conservatively at 80-100% capacity; heed overcrowding/aggression alerts and test combinations.[1][3][5]
• Use net capacity: multiply max volume by 0.85-0.9 for decor.[7][8]
• Monitor ammonia/nitrates weekly, do regular water changes, and add fish gradually while re-calculating.[4][6]
• Avoid exceeding limits even with extra filters, as nitrate buildup accelerates.[6][7]

Sources

• aquanory.com
• 907heatingplumbing.com
• youtube.com
• hygger-online.com
• swellukhelp.zendesk.com