Hydro Habitats Guide Library
Aquarium Tools
Free aquarium calculators—no account required. Explore water volume, flow, reserve capacity, filled weight, and alkalinity units. Results are estimates or unit conversions, not livestock prescriptions, pump guarantees, or structural approval.
Sump Power-Off / Reserve Calculator
Estimate display drain-down and compare it with the sump's unused space up to its safe maximum level.
Example calculation
Illustrative—not a recommendation: A 48 by 18 inch display dropping 1 inch drains 864 / 231 = 3.740 US gallons. A 36 by 16 inch sump with 4 inches of unused safe depth has 2304 / 231 = 9.974 US gallons reserve. A separately estimated 2 US gallon plumbing allowance raises total drain-down to 5.740 US gallons; verify with a real power-off test.
Read sump reserve planning.
Estimate
Required safety test: A positive estimate is not a guarantee. Switch off the return pump and verify in person that the complete system drains without overflowing the sump. A check valve is not a substitute for adequate reserve capacity or testing.
How the sump estimate is calculated
Display drain volume assumes a rectangular inside footprint and uniform water-level drop; substrate, rock, overflow and plumbing geometry can change the actual drain-down. The separate plumbing/back-siphon allowance is supplied by you. Sump reserve uses its rectangular inside footprint multiplied by the depth between the operating and maximum safe water levels.
Return Pump / Head-Loss Estimator
Estimate the operating point where your pump's manufacturer curve meets estimated plumbing losses.
Example calculation
Illustrative—not a recommendation: A synthetic curve (not a real pump model) might contain 0 US GPH at 15 ft, 300 at 12 ft, 600 at 7 ft, and 900 at 0 ft. Enter those manufacturer-style flow/head pairs, then add static lift, pipe inside diameter and length, and one fitting-loss method. The sample form values produce an estimated intersection of about 671 US GPH. Use the Load illustrative example button to see the complete workflow; replace every sample with data for your own pump and plumbing.
Read return-pump sizing and curve limits.
Estimated operating point
Estimate only: This does not guarantee pump output or replace measured flow. The curve must match the exact pump setting, and the calculator never extrapolates beyond entered points. If there is no intersection, check the curve and plumbing data or add manufacturer points that bracket the operating point.
Calculation method and limitations
The estimate uses Darcy–Weisbach pipe and fitting losses, a general friction-factor approximation, water properties near 20°C, and linear interpolation only between user-supplied manufacturer data for the same pump/control setting. It assumes a simple return path; valves, filters, manifolds, dirty equipment, unusual fittings, complex manifolds, equipment restrictions, and measurement error may add losses. A flow meter or measured pump data is more reliable.
Alkalinity Unit Converter
Convert one alkalinity result among dKH, meq/L, and ppm as calcium carbonate without changing the measurement.
Example calculation
8 dKH × 17.848 = 142.784 mg/L as CaCO3; dividing by 50 gives 2.85568 meq/L (about 2.856). This converts units, not a dose.
Read KH and alkalinity interpretation.
Equivalent alkalinity
Conversion basis and limitations
1 meq/L = 50 mg/L as CaCO3; 1 dKH = 17.848 mg/L as CaCO3 (therefore about 0.357 meq/L). ppm is treated as mg/L for these dilute aquarium-water measurements. Test methods and what they measure can differ; use the unit stated by the test or instrument. This converts units; it does not calculate a chemical dose.
Aquarium Filled-Weight Estimator
Estimate water mass from actual operating volume, then add known tank, stand, substrate, rock, and equipment weights.
Example calculation
Illustrative—not a recommendation: 100 actual US gallons of freshwater × 3.785411784 L/US gal × 0.9982 kg/L × 2.20462262185 lb/kg = about 833.04 lb of water (833 lb using rounded 8.33 lb/gal). Add known tank, stand, rock, substrate and equipment weights separately; an empty component field means unknown.
Read aquarium dimensions, support and weight planning.
Estimated operating weight
Structural limitation: This estimate cannot determine whether a floor, stand, or building structure can safely support the aquarium. For significant loads or uncertain structures, obtain a qualified structural evaluation. Empty component fields are unknown and excluded, so an incomplete total may be understated.
Water-density assumptions
At approximately 20°C, freshwater is estimated at 0.9982 kg/L and standard-ocean saltwater at about 1.025 kg/L. Actual water density varies with temperature and salinity. The weight calculation converts actual display and sump water volume to mass using the selected water type, then adds entered component weights.
Water Change Calculator
Calculate the volume to remove and replace for one chosen change using actual system water volume.
Example calculation
Illustrative—not a recommendation: 100 US gallons × 25% = 25 US gallons removed and replaced. After one ideal well-mixed exchange, 75 US gallons of the original water remain. This is not a universal percentage or a guaranteed pollutant endpoint.
Read nitrate reporting and dilution limits.
Single water change
Scope: This calculates one selected water change. It does not prescribe a universal percentage or estimate nitrate reduction, treatment, or pollutant endpoints.
Single-change assumptions
A single change removes and replaces equal volumes, leaving the system at its starting water volume. “Original water remaining” is the ideal well-mixed remainder immediately after that one exchange. For a sequence of changes, each exchange acts on the remaining concentration rather than adding percentages.
Aquarium Turnover Calculator
Calculate turnovers per hour from system volume and flow, or find the flow for a selected turnover rate.
Example calculation
Illustrative—not a recommendation: 500 US GPH / 100 actual US gallons = 5 turnovers per hour. Return flow through a sump is distinct from in-tank circulation; a turnover value does not demonstrate even flow or adequate oxygen.
Read water-movement distribution and calm zones.
Turnover estimate
Interpretation: Turnover is flow divided by system volume. It describes nominal hourly volume movement, not how evenly water reaches livestock or surfaces. For reef systems, sump-return turnover and separate powerhead/wavemaker circulation are different flows; do not add them or treat a turnover figure as a universal ideal.
Methods and References
Equations and conversion constants are standard dimensional or engineering relationships; the estimation limits are stated with each tool.
- Losses and Friction Factors NPTEL fluid-mechanics lecture; Darcy–Weisbach head loss and friction-factor context.
- Friction-Factor Equation Spans All Fluid-Flow Regimes Stuart W. Churchill, Chemical Engineering, 1977; original friction-factor correlation.
- Total Alkalinity U.S. Environmental Protection Agency; alkalinity reported as calcium carbonate equivalents.
- Alkalinity and Acid-Neutralizing Capacity U.S. Geological Survey technical reference on alkalinity units and equivalents.
- Facts About Water U.S. Geological Survey; freshwater density context.
- World Ocean Database 2018 Notes NOAA National Centers for Environmental Information; standard-ocean seawater density convention.
- Thermodynamic Properties of Water National Institute of Standards and Technology; IAPWS formulation and freshwater density by temperature.
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