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. If this is the route you want, see the full PPS-Pro recipe and dosing schedule for the exact two-bottle mix and daily dose.
- 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.
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.
Gear this guide uses
Whichever method you pick, you either mix dry salts or buy an all-in-one bottle — and verify with CO₂ on a high-tech tank.
- Run EI or PPS-Pro cheaply with dry aquarium fertilizer salts (KNO₃, KH₂PO₄, CSM+B).
- Prefer bottles? Reach for an all-in-one liquid plant fertilizer like Seachem Flourish or NilocG Thrive.
- On a CO₂ tank, watch your injection with a CO₂ drop checker.
Some links below are affiliate links — if you buy through them, Moon Dog may earn a small commission at no extra cost to you. We only point to gear we'd actually use.
Sources
General hobbyist guidance — dial in against your own plant response and algae, and adjust gradually.