Aquarium water change calculator

A 10–30% weekly change is a starting range, adjusted by water tests and livestock needs. The table uses 85% of nominal capacity, not geometric volume. Bucket counts are fractional volume equivalents; use safe fill marks and allow carrying headroom. Larger emergency changes may be needed for unsafe water, with temperature and chemistry matched.

Worked example: 20 gallon long

20 nominal gal × 0.85 = 17 estimated water gal. × 0.25 = 4.25 gal (16.09 L). Divide by 5 = 0.85 bucket equivalents.

Aqueon water maintenance

Choose a tank size

• 2.5 gallon12 × 6 × 8 in
• 5 gallon16 × 8 × 10 in
• 5.5 gallon16 × 8 × 10 in
• 10 gallon20 × 10 × 12 in
• 13 gallon widescreen24 × 8 × 19 in
• 15 gallon24 × 12 × 12 in
• 15 gallon column13.75 × 13.62 × 25 in
• 20 gallon high24 × 12 × 16 in
• 20 gallon long30 × 12 × 12 in
• 20 gallon extra high20 × 10 × 24 in
• 25 gallon24 × 12 × 20 in
• 29 gallon30 × 12 × 18 in
• 30 gallon36 × 12 × 16 in
• 33 gallon long48 × 13 × 13 in
• 37 gallon30 × 12 × 22 in
• 38 gallon36 × 12 × 20 in
• 40 gallon breeder36 × 18 × 16 in
• 40 gallon long48 × 12 × 16 in
• 45 gallon36 × 12 × 24 in
• 50 gallon36 × 18 × 19 in
• 55 gallon48 × 13 × 21 in
• 60 gallon breeder48 × 18 × 16 in
• 65 gallon36 × 18 × 24 in
• 75 gallon48 × 18 × 21 in
• 90 gallon48 × 18 × 24 in
• 110 gallon48 × 18 × 30 in
• 120 gallon48 × 24 × 24 in
• 125 gallon72 × 18 × 21 in