Calculator
Use measured phosphate levels to size a remover dose.
Example data table
| Scenario | Volume (L) | Current (mg/L) | Target (mg/L) | Capacity (mg per mL) | Efficiency | Safety | Estimated dose (mL) |
|---|---|---|---|---|---|---|---|
| Raised-bed reservoir | 200 | 0.60 | 0.10 | 450 | 85% | 10% | 0.29 |
| Greenhouse tote | 500 | 1.20 | 0.10 | 450 | 85% | 10% | 1.58 |
| Small pond edge tank | 1,200 | 0.35 | 0.05 | 300 | 80% | 15% | 1.73 |
Examples use typical efficiency and safety settings. Always follow product labels and retest water before repeating.
Formula used
- Removal needed (mg/L) = max(0, Current − Target)
- Total removal (mg) = Removal needed × Volume(L)
- Effective capacity (mg per unit) = Label capacity × (Efficiency ÷ 100)
- Units per treatment = (Total removal ÷ Effective capacity) × (1 + Safety ÷ 100)
- Total units = Units per treatment × Treatments
How to use this calculator
- Measure phosphate in your water source using a reliable test.
- Enter the water volume and select the correct unit.
- Enter current and target phosphate values in mg/L.
- Read your remover label and enter “mg removed per unit”.
- Choose a realistic efficiency and a small safety margin.
- Press Submit to see dosing above the form.
- Download CSV or PDF to store treatment notes and costs.
- Apply, circulate, then retest before repeating treatments.
Practical phosphate targets for garden water
Phosphate (PO4) fuels algae, biofilm, and cloudy storage in barrels and pond-edge tanks. Lowering readings reduces slimy buildup on emitters, improves oxygen transfer, and supports stable microbial balance. Use your own test results; trends matter more than single samples.
What the dose represents in measurable terms
This calculator converts concentration change into mass: mg/L × liters = mg. If you lower 1.20 mg/L to 0.10 mg/L in 500 L, the removal target is 1.10 mg/L, or about 550 mg of phosphate. Your product “capacity” must match the dose unit you select.
Why efficiency and safety margins are included
Real systems seldom hit label performance. Organics, suspended solids, and incomplete circulation reduce binding or precipitation. Efficiency adjusts capacity downward to reflect field conditions. Safety margin adds a small buffer for test variability and mixing loss, helping you land closer to the target after retesting.
Using split treatments to avoid overshooting
Instead of one large application, many growers prefer two to four smaller treatments. Split dosing improves control, reduces the risk of rapid chemistry shifts, and allows you to stop early if readings fall faster than expected. Enter the number of treatments to see a planned total dose.
Cost and recordkeeping for repeatable maintenance
When you add price per unit, the tool estimates cost per treatment and total cost. Exporting CSV or PDF creates consistent logs with volume, starting level, target, and calculated dose. Over time, these records help you refine efficiency assumptions and select products with better performance per cost.
FAQs
1) What unit should I use for phosphate readings?
Use mg/L (often the same as ppm for water tests). Keep the same unit for current and target values so the calculator can compute removal accurately.
2) How do I find “mg removed per unit” on a label?
Look for dose guidance tied to a measured reduction. Convert it to total mg removed per mL or gram. If the label states a reduction per 1000 L, multiply by liters to get mg per unit.
3) Why does the calculator ask for efficiency?
Efficiency models real-world losses from organics, debris, and imperfect circulation. Lower efficiency increases the recommended dose so you’re less likely to under-treat.
4) Can I use this for ponds or hydroponic reservoirs?
Yes, if you can measure volume and phosphate reliably. For sensitive systems, use split treatments and retest between doses to avoid rapid shifts.
5) What if my current value is already below target?
The calculator returns zero removal needed and suggests no dosing. Save the export as a baseline reading and monitor for future increases.
6) How soon should I retest after dosing?
Retest after thorough circulation and enough contact time for your remover type. Many users check within a few hours to a day, then adjust the next treatment based on the new reading.