EI vs. PPS-Pro vs. PMDD: which dosing method?

Three approaches to feeding a planted tank — what each one actually does, and who it suits.

Planted-aquarium fertilizing is famously tribal: people self-identify as "EI" or "PPS-Pro." But the three named methods are really just different answers to one question — how do you supply nutrients without letting them build up? Here's what separates them.

The three methods

Method	Philosophy	Schedule	Water change
EI (Estimative Index)	Dose nutrients in excess so plant uptake is the limiting factor, never the water column	Macros + micros on alternating days (~3×/week)	50% weekly — required
PPS-Pro	Dose to roughly match daily uptake — little to no excess	Small daily dose (~1 mL per 10 gal)	Optional
PMDD	The 1996 forerunner of both — lean daily trace dosing, limit phosphate	Daily microdose	Optional

How to choose

EI (Tom Barr) suits high-tech tanks — pressurized CO₂, strong light, fast growth. You stop worrying about precise numbers and let the weekly 50% water change reset everything. Simple to run, uses more fertilizer, and the big water change is non-negotiable.
PPS-Pro (ChrisCowAU / Edward) suits people who want fewer or smaller water changes and a steady daily routine. It doses closer to what the plants actually use, so less accumulates — but it's less forgiving if your estimate is off.
PMDD (Sears–Conlin, 1996) is mostly of historical interest now — the method EI and PPS-Pro grew out of. Few hobbyists run it as-is today.

The brand shortcut.

Most all-in-one liquid fertilizers map to a method: 2HR Aquarist's APT e is sold as an "EI formula," APT 1 as an ADA-lean (leaner) blend; NilocG publishes both EI and PPS-Pro schedules for Thrive. So picking a bottle is often picking a method without realizing it.

Don't forget the dilution rule

Whatever method you choose, low-tech tanks without CO₂ generally want the lean end (PPS-Pro or a reduced EI), because slow-growing plants can't use a heavy nutrient load and the excess just feeds algae. High light + CO₂ is what justifies EI's heavier dosing.

Aquascape doses any of these for your exact tank

Pick EI, PPS-Pro, PMDD, or a custom target, enter your tank volume, and Aquascape gives the dry-salt weights or brand-aware liquid schedule (Seachem Flourish, NilocG Thrive, 2HR APT, GLA) — plus CO₂-from-pH/KH and GH/KH tools. Pay once, no subscription, works offline.

Get Aquascape on the App Store

Sources

General hobbyist guidance — dial in against your own plant response and algae, and adjust gradually.