Aquarium Water Change Calculator

Water change volume and frequency from bioload.

Tank Volume (gallons)

Current Nitrate (ppm)

Target Nitrate (ppm)

Weekly Nitrate Rise (ppm)

Tab to move between fields

Immediate Change (%)

Immediate Change (gallons)

22.5

Weekly Maintenance (%)50

Weekly Change (gallons)15

Post-Change Nitrate (ppm)10

Schedule Intensity3

How to Use This Calculator

How the result changes with Current Nitrate (ppm)

Tank Volume (gallons): Total water volume of the aquarium in US gallons.
Current Nitrate (ppm): Your current nitrate reading. Safe range is typically under 20 ppm for freshwater.
Target Nitrate (ppm): Desired nitrate level after the water change. 10-20 ppm is a common target.
Weekly Nitrate Rise (ppm): How many ppm nitrate rises per week from feeding and bioload.

Immediate Change (%): Percentage of water to change now to reach your target nitrate.
Immediate Change (gallons): Volume of water to remove and replace now.
Weekly Maintenance (%): Recommended weekly water change percentage to maintain nitrate below 20 ppm.
Weekly Change (gallons): Weekly water change volume for ongoing maintenance.
Post-Change Nitrate (ppm): Expected nitrate level immediately after the water change.
Schedule Intensity: 1 = Light (biweekly OK), 2 = Standard (weekly), 3 = Heavy (twice weekly or reduce stocking).

Identify Input Parameters
4 parameters
Tank Volume (gallons) = 30, Current Nitrate (ppm) = 40, Target Nitrate (ppm) = 10, Weekly Nitrate Rise (ppm) = 10 = 4 input(s) provided
Calculate Immediate Change
Immediate Change
75 = 75
Calculate Immediate Change
Immediate Change = (tankVolume * changePercent) / 100
22.5 = 22.5
Calculate Weekly Maintenance
Weekly Maintenance
50 = 50
Calculate Weekly Change
Weekly Change = (tankVolume * weeklyChangePct) / 100
15 = 15