Beginner low-tech planted tank dosing

Without injected CO₂, plants grow slowly. They need far less fertilizer than an EI sheet suggests, and overdosing mostly feeds algae.

A simple starting plan

Once a week, after a 25–30 % water change, dose a small all-in-one: about 5 ppm NO₃, 0.5 ppm PO₄, 5 ppm K and 0.1 ppm Fe added per week. Open it for 20 US gal.
If fish load is heavy, you may need no nitrate at all; fish waste supplies it.
Root feeders (swords, crypts) benefit from root tabs in the substrate.
Watch new leaves for 2–3 weeks before changing anything.

Commercial products for low-tech

Tropica Premium Nutrition (no N or P) is aimed at tanks with few plants and many fish; Specialised Nutrition adds N and P for denser planting. Seachem Flourish is a micro/trace supplement, used once or twice a week. See exact doses for your volume in the product library.

Algae checklist

Light duration of 6–8 hours is usually enough.
More fast plants (floaters, stems) out-compete algae.
Cut doses in half before adding chemicals to fight algae.

A weekly low-tech dosing schedule

Day	Do this
Water-change day (e.g. Sunday)	Change 25–30 % of the water, then add the whole week's dose: dry salts at the low-tech rate, or a liquid such as Tropica (6 mL per 50 L) or Seachem Flourish (5 mL per 250 L).
Mid-week (optional)	Seachem's label allows a second Flourish dose; skip it if you see algae.
Other days	Nothing. Check plants and top up evaporation with plain water.
Every few months	Replace root tabs for heavy root feeders, following the tab's label.

Grams for your size: 10, 20, 40, 55 or 75 gallon (see the low-tech column), or download calendar reminders from the calculator.

Shrimp in low-tech tanks

Low-tech tanks are popular for shrimp. Keep trace doses lean, since copper is toxic to invertebrates at low levels, and check your tap water's copper.

FAQ

How often should I fertilize a low-tech planted tank?

Once a week after the water change is enough for most tanks without CO₂. Plants grow slowly, so daily or EI-level dosing mostly feeds algae.

Does a low-tech tank need fertilizer at all?

Not always. A heavily stocked tank, or one with a nutrient-rich soil substrate, may supply enough nitrogen and phosphate; it may only need micros and root tabs. Add fertilizer when new leaves show deficiency signs.

Can I use EI in a low-tech tank?

Full EI is designed for high light and CO₂. In a low-tech tank use about a quarter or less, which is what the low-tech preset does, with a smaller weekly water change.

Where to buy · Retailer links coming soon.

Open the dosing calculator More guides

Sources

Written in our own words from the sources above. Numbers are educational starting points; check product labels and your water.