PPS-Pro: the lean daily dosing method and its targets
Short answer
PPS-Pro uses two bottles: macros (29 g K2SO4, 33 g KNO3, 3 g KH2PO4 and 20 g MgSO4 in 500 mL) and a trace mix (29 g in 500 mL) [2]. The daily dose is 1 mL of macros and 0.5 mL of traces per 10 US gallons or 40 L, which its author states adds 1 ppm NO3, 0.1 ppm PO4, 1.33 ppm K, 0.1 ppm Mg and 0.05 ppm Fe a day [3]. It aims at a lean water column, around 5–10 ppm nitrate [4].
What PPS-Pro is
PPS stands for Perpetual Preservation System, a pair of dosing methods published by an aquarist who signs as Edward. Its introduction describes two systems: PPS-Classic, which uses periodic testing and a calculator to set doses, and PPS-Pro, the simplified version that “doesn’t need testing and tweaking” and works with all lights and substrates, with or without water changes [1, 2]. PPS-Pro is the one most aquarists mean when they name the method.
The recipe
Two bottles, made up with soft water [2]:
| Bottle | Per 500 mL |
|---|---|
| #1 macros | 29 g K2SO4, 33 g KNO3, 3 g KH2PO4, 20 g MgSO4 |
| #2 micros | 29 g of a dry trace-element mix |
The chemicals page lists the salts and names several trace mixes the author considers suitable, including EDTA and EDTA+DTPA micronutrient mixes and CSM+B [3].
The dose and what it adds
Dose daily: 1 mL of the macro bottle and 0.5 mL of the micro bottle per 10 US gallons or 40 L, before the lights come on [3]. The author states that this adds 1 ppm NO3, 0.1 ppm PO4, 1.33 ppm K, 0.1 ppm Mg and 0.05 ppm Fe per day. For lower light the dose is halved; for very high light it is doubled [3].
Those stated figures can be checked with the molar-mass method from IUPAC atomic weights [7]. One milliliter of the macro bottle holds 66 mg of KNO3 (33 g ÷ 500 mL); in 40 L that is 1.65 mg/L of KNO3, and 61.3 % of it is nitrate, so 1.01 mg/L NO3. The same working gives 0.10 mg/L PO4 and, summing the three potassium salts, 1.33 mg/L K. Magnesium only comes out at the stated 0.1 mg/L if “MgSO4” means Epsom salt (the heptahydrate); anhydrous magnesium sulfate would give twice as much. The EI and PPS-Pro planner runs this check for your tank size.
Iron depends on the trace mix. With a mix that is about 7 % iron, 0.5 mL of a 29 g / 500 mL solution in 40 L gives about 0.05 mg/L, matching the stated figure.
The targets: a lean water column
PPS separates two things that are easy to confuse: the daily dose and the water-column level. Its “Plant requirements” page gives the levels it aims to maintain [4]:
| Nutrient | Water-column range |
|---|---|
| NO3 | 5–10 ppm |
| PO4 | 0.1–1 ppm |
| K | 5–20 ppm |
| Mg | 2–5 ppm |
| Ca | 20–30 ppm |
| CO2 | 10–20 ppm (with injection, for higher light) |
The same page explains the logic with an example: a water column at 10 ppm nitrate while 1–2 ppm is added daily is what keeps the aquarium stable [4]. The nitrate page estimates daily plant uptake at about 1 ppm of nitrate plus fish waste, and warns that nitrate should never fall to zero in a fully planted tank [5].
How it differs from EI
Both methods use the same salts, but they set them up in opposite ways.
| PPS-Pro | EI | |
|---|---|---|
| Dose size | close to estimated daily uptake | deliberate surplus |
| Frequency | daily | about three times a week |
| Water changes | optional | 50 % weekly, part of the method |
| Typical nitrate target | 5–10 ppm | 10–30 ppm (EI Light) |
| CO2 target | 10–20 ppm | 25–35 ppm |
Sources: [4, 3]; EI figures from the EI guide.
Over a week, PPS-Pro at the standard dose adds 7 ppm of nitrate. Without water changes, where the level settles depends entirely on uptake, which is why the author suggests monitoring nitrate or conductivity from time to time and adjusting [3]. With a weekly water change of fraction f and no uptake at all, the ceiling would be 7 ÷ f ppm; the water-change calculator shows the curve.
Adjusting for your tank
The author’s own adjustments are:
- Light: half dose for low light, double for very high light [3].
- High nitrate from fish or tap water: switch to the nitrate-free macro bottle: 40 g K2SO4, 3 g KH2PO4 and 20 g MgSO4 per 500 mL, no KNO3, same dose. Its stated daily contribution is 0 ppm NO3, 0.1 ppm PO4, 1 ppm K and 0.1 ppm Mg [5].
- Water changes: the author argues that a well-planted tank with a reasonable fish load needs fewer water changes than often advised, and that the parameter that drifts fastest should set the minimum change rate [6].
PPS-Pro also states its intended scope plainly: heavily planted aquariums with a reasonable fish load. “An aquarium with one Cryptocoryne and a Goldfish will not work smoothly” [3].
Questions
When should PPS-Pro be dosed?
Daily, at the same time, before the lights come on, according to its author; both bottles can be dosed together into moving water [3].
What if my nitrate is already high?
The author publishes a nitrate-free macro recipe (40 g K2SO4, 3 g KH2PO4, 20 g MgSO4 per 500 mL, no KNO3) for tanks with many fish or nitrate-rich tap water, dosed the same way [5].
Calculators for this
- EI and PPS-Pro plannerTurn the Estimative Index and PPS-Pro, as their authors published them, into grams or milliliters for your tank, with the build-up each schedule produces.
- Water-change dilutionWhat a water change does to nitrate, phosphate, TDS or any dissolved level, the change needed to hit a target, and where weekly dosing settles.
- Stock solutionPlan a bottle of dissolved fertilizer salts: what each milliliter adds to your tank, how long the bottle lasts, and whether the salts will dissolve.
Related guides
- FertilizersCalcium, magnesium and GH for aquarium plantsWhat GH measures, how much calcium and magnesium one degree represents, how Epsom salt and GH boosters change it, and the targets EI, PPS and Aquasabi give.
- FertilizersEstimative Index (EI) dosing: what the method prescribesEI as Tom Barr wrote it up: dose a surplus three times a week, change 50 % of the water weekly, and why that caps build-up at twice the weekly dose.
- FertilizersHow ppm from dry fertilizer salts is calculatedThe molar-mass arithmetic behind every dosing chart: grams of salt to mg/L of nitrate, phosphate or potassium, with worked examples and the common traps.
- FertilizersMixing dry-salt stock solutions: solubility, separation and storageHow to turn dry fertilizer salts into a dosing bottle: solubility limits from PubChem, why phosphate and iron go in separate bottles, and storage and safety.
Sources
- Perpetual Preservation System (introduction). Edward, Perpetual Preservation System. PPS-Pro and PPS-Classic described by their author. Accessed October 12, 2026.
- PPS-Pro. Edward, Perpetual Preservation System. Recipe for 500 mL bottles; designed for aquascapers, all lights and substrates, with or without water changes. Accessed October 12, 2026.
- Chemicals & Dosing. Edward, Perpetual Preservation System. Chemicals list; dose 1 mL macros and 0.5 mL micros per 10 gal or 40 L daily; stated daily ppm; light scaling; dose before lights on; difference from PPS-Classic. Accessed October 12, 2026.
- Plant requirements. Edward, Perpetual Preservation System. Water-column ranges: NO3 5–10, PO4 0.1–1, K 5–20, Mg 2–5, Ca 20–30 ppm; CO2 10–20 ppm with injection; daily dose vs water-column level. Accessed October 12, 2026.
- Nutrient imbalance N: NO3 too low / high. Edward, Perpetual Preservation System. Daily plant uptake about 1 ppm NO3; NO3 should not drop to zero; nitrate-free macro recipe. Accessed October 12, 2026.
- Water Changes. Edward, Perpetual Preservation System. The author's view on water changes in planted tanks. Accessed October 12, 2026.
- Abridged standard atomic weights. IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW). Accessed October 12, 2026.