PPS-Pro dosing method explained

What PPS-Pro is and who it suits

PPS stands for Perpetual Preservation System, a dosing approach published by Edward, a hobbyist who maintains the aquaticplantfertilizer site. The Pro version simplifies the original to two premixed solutions dosed daily in small, fixed amounts. The goal is a steady, low nutrient water column that plants draw from continuously, rather than the high weekly peaks of Estimative Index dosing.

It suits people who do not want a weekly 50 percent water change, who keep livestock sensitive to nitrate, or who prefer to dose the same small amount every morning instead of remembering which salt is due on which day. It is also the easier method for a small tank, because milliliters of solution are easier to measure than 1/32 teaspoon of dry salt.

It is not a starvation method. The daily dose is sized to match a moderately lit, CO2 injected tank's daily uptake, and the published guidance scales it up for high light and down for low light.

Mixing the two stock solutions

Solution 1 (macros), per 1 liter of distilled or reverse osmosis water: 14.3 g potassium nitrate (KNO3), 1.5 g monopotassium phosphate (KH2PO4), and 29.4 g potassium sulfate (K2SO4). These are the recipes reproduced in the Gensou PPS-Pro dosing guide.

Solution 2 (traces), per 1 liter of distilled or RO water: 32.5 g of a trace mix such as CSM+B (a chelated micronutrient blend with boron) and 29.4 g of magnesium sulfate heptahydrate (Epsom salt). Some mixers leave the magnesium out of the trace bottle and add it to the macro bottle instead, but the standard recipe keeps them together.

Dissolve fully, label each bottle, and store in the dark. Distilled or RO water matters more for the trace bottle, where tap water minerals and chlorine can precipitate the chelated iron. A weak preservative or refrigeration extends the life of the trace solution; the macro solution keeps for months at room temperature.

The daily dose and what it adds

Standard dose: 1.0 ml of Solution 1 and 0.5 ml of Solution 2 per 10 gallons (about 40 liters) of tank water, every day, ideally before the lights come on. Green Leaf Aquariums lists the same figures, 1.0 ml (20 drops) of macros and 0.5 ml (10 drops) of micros per 10 gallons daily.

Each standard dose raises the water by approximately 1.0 ppm NO3, 0.1 ppm PO4, 1.33 ppm K, 0.1 ppm Mg, and 0.05 ppm Fe from the trace mix. Over a seven day week that is 7 ppm NO3, 0.7 ppm PO4, 9.3 ppm K, 0.7 ppm Mg, and 0.35 ppm Fe, roughly a third of a standard EI week.

The method's author scales the dose by light. Low light: 0.5 ml of Solution 1 and 0.25 ml of Solution 2 per 10 gallons, giving a weekly accumulation of about 7 ppm NO3 and 0.7 ppm PO4 with a 50 percent weekly water change. Medium light: the standard 1 ml and 0.5 ml, capping at about 14 ppm NO3, 1.4 ppm PO4, 18 ppm K. High light: 2 ml and 1 ml, capping at about 28 ppm NO3, 2.8 ppm PO4, 36 ppm K, 2.8 ppm Mg, and 1.4 ppm Fe.

Worked example: a 29 gallon tank

A 29 gallon tank holds about 26 gallons of water after substrate and hardscape. Using 26 gallons: 26 divided by 10 is 2.6, so the standard daily dose is 2.6 ml of Solution 1 and 1.3 ml of Solution 2. Round to 2.5 ml and 1.25 ml, which are easy marks on a syringe.

That dose adds about 1 ppm nitrate and 0.1 ppm phosphate per day. A 1 liter macro bottle lasts 1,000 divided by 2.5, which is 400 days. The trace bottle lasts 800 days at 1.25 ml a day, longer than the iron chelate stays good, so mix the trace solution at half strength or half volume and remake it every few months.

Benchlet's aquarium dosing calculator does this division from the tank's net volume and lets you save the tank profile, so the 2.5 ml and 1.25 ml figures are on screen the next time you refill a bottle rather than recomputed by hand.

Water changes under PPS-Pro

The original guidance treats water changes as conditional rather than weekly. The published rule is to change water when the aquarium's conductivity exceeds the tap water's conductivity by more than 100 microsiemens, which indicates dissolved solids from fertilizer and waste have accumulated. Green Leaf Aquariums lists a 50 percent weekly change as optional for PPS-Pro.

Most hobbyists still do a moderate weekly change of 25 to 50 percent for fish health and organic waste removal. With a 50 percent weekly change and the standard dose, the nitrate ceiling is about 14 ppm, which is the figure the method's author lists for medium light. Without any change the level drifts upward by however much the plants fail to consume, so a conductivity meter or an occasional nitrate test is a good check.

PPS-Pro compared with EI

Both methods use the same dry salts and both work. EI doses about three times as much and relies on a mandatory 50 percent weekly change to cap accumulation; PPS-Pro doses a small amount daily and lets accumulation stay low enough that water changes are optional. EI is more forgiving of a missed dose because there is always a surplus; PPS-Pro is more forgiving of a missed water change because there is never much surplus.

Choose EI for a high light, heavily planted, CO2 injected tank where growth is fast and water changes are routine. Choose PPS-Pro for a moderately lit tank, a tank with shrimp or sensitive fish, a small tank where dry salt measurement is impractical, or a maintenance routine that cannot guarantee a large weekly change. Many aquarists run PPS-Pro amounts on an EI style alternate day schedule; the salts do not care which label is on the bottle.

Frequently asked questions

Sources

• Perpetual Preservation System: Chemicals and Dosing (original author's dosing levels by light)
• Green Leaf Aquariums: Dry Fertilizer Dosing Guide (PPS-Pro dose and ppm)
• Gensou: PPS-Pro Dosing Method Guide (stock solution recipes)