Nutrient dosing
EI, EI-lite, PPS-Pro, and commercial liquid dosing for planted tanks. Reads your saved plant roster to suggest a method.
Manual overrides
By default the calculator reads your saved plant roster (if you've used the stocking calc) to recommend a method. Toggle the override here if you want to ignore it.
What this does
Pick a dosing method, enter your tank volume, and get the per-dose amount of each salt or ml of commercial fertiliser. If you've used the stocking calculator and saved a plant roster, the calculator reads it and suggests a method based on what you're keeping.
A heavily-planted high-light tank with rotala wallichii needs different dosing than a tank with three anubias on a piece of driftwood. The recommendation engine separates the two.
The methods
EI (Estimative Index) is the regimen for high-tech tanks. Dose a deliberate excess of every nutrient, do 50% weekly water changes to reset accumulation. The water change is the safety mechanism: without it, you'd build up nitrate and phosphate past algae-triggering levels. The math is set so that uptake doesn't have to be precisely matched.
EI Lite is half-dose EI for medium-tech or shrimp tanks. Same salts, half the grams, smaller water changes. Less of a swing. Works in shrimp tanks where full EI's nitrate jumps would stress sensitive species.
PPS-Pro (Perpetual Preservation System) is the daily-dose approach. Target specific levels and maintain them with daily dosing, instead of cycling through excess + reset. No mandatory water changes for nutrient reasons. More daily discipline, less weekly work. The daily grams are too small to weigh, so you mix a stock solution and dose by the ml.
NilocG Thrive is the most popular all-in-one liquid. One bottle covers macros and micros at sensible ratios. One pump (2 ml) treats 10 gal (38 L). Easy. Gets expensive past 200 L or so of tank volume, where a year of bottles costs more than a set of DIY salts.
Seachem Flourish Comprehensive is trace elements only, despite many keepers using it as a complete fertiliser. It is not. The full Seachem line includes separate Flourish Nitrogen, Phosphorus, and Potassium bottles. Adding only Comprehensive leaves your plants starved of N, P, K.
Tropica Premium is the European-side equivalent of Flourish Comprehensive: trace elements. Pair with Tropica Specialised (the green-cap bottle) for macros.
Why DIY beats commercial at scale
For a 75L tank on full EI:
- DIY salts: about 5 g a week across KNO3, KH2PO4, K2SO4, and CSM+B. KNO3 goes fastest at under 3 g a week, so a 1 kg bag lasts years. The four bags cost $40-60 up front.
- Thrive: 4 ml per dose, twice a week. Two pumps each time, 8 ml a week. A 500 ml bottle ($25-30) lasts over a year.
At 75 L the two are close: $25 or so a year for the bottle against a one-off $50 for salts that outlast the tank. Scale changes that. At 300 L Thrive is 32 ml a week, a bottle every four months, $90 or so a year, while the same bags of salts still last a year and a half at minimum. With several tanks the gap widens again.
The barrier is buying a 0.01g jewellery scale ($15-30) and four little salt jars. Once that's done, a dose is four quick weighings.
Why a 0.01g scale matters
KH2PO4 doses in EI are around 0.1-1g per week. A 1g scale rounds these to 0 or 1, with massive error margins. A 0.01g jeweller's scale resolves a 0.15g dose accurately. Eyeballing or estimating leads to algae blooms (too much) or starved plants (too little).
The scale pays for itself in saved frustration within a month.
What algae blooms tell you
Algae outbreaks in a dosed tank usually mean one of three things:
Too much light, not enough CO2. Light drives photosynthesis. Photosynthesis needs CO2. If light is high and CO2 is low, plants can't absorb the macros you're dosing fast enough, and the excess feeds algae. The fix is more CO2 or less light, not less dosing.
Inconsistent dosing. A week of EI doses then two weeks of nothing causes algae more reliably than steady half-dosing. Set a phone calendar reminder.
Stale water with no water changes. EI and EI-lite both depend on the weekly water change to reset accumulation. Skipping water changes builds up unused nutrients, organics, and algae triggers. PPS-Pro is the exception (no mandatory change), but it requires more careful daily uptake-matching.
When to skip dosing entirely
Tanks with low plant load (a few anubias, java fern, some moss) often don't need any added fertiliser. Fish food provides nitrogen and phosphorus; tap water provides potassium and trace elements. Adding nutrients to a tank that doesn't need them is one of the fastest paths to algae.
The Walstad method (the natural planted tank) deliberately doesn't dose. Heavy plant mass, organic-rich substrate, light fish stocking, slow growth. If you find dosing tiring, the natural method is worth reading about.
Related tools
- CO2 calculator - Check dissolved CO2 from pH and KH. Dosing past what your CO2 supports feeds algae, not plants.
- Lighting - PAR at the substrate sets the uptake you're feeding.
- Planted tank planner - Substrate and water-parameter check for the same roster.