KNO3 Potassium Nitrate Dosing Guide: Planted Tank Recipe

Potassium nitrate is the workhorse macro-nutrient salt that drives most planted tank fertiliser routines, from EI to lean and everything between. This kno3 potassium nitrate dosing guide from Gensou Aquascaping at 5 Everton Park covers the chemistry, the recipes that actually work in soft Singapore tap water, and the dosing schedules that hit your nitrogen and potassium targets without stockpiling either. KNO3 is cheap, stable in solution and predictable; once you understand the contribution per gram per litre, the rest is arithmetic.

Why KNO3 Matters in Planted Tanks

Stem plants and demanding species pull nitrogen and potassium hard during peak growth, and tank inhabitants rarely produce enough nitrate to keep up. Singapore’s PUB tap water arrives at near-zero nitrate after treatment, so your plants depend entirely on what you dose. KNO3 delivers both nutrients in one salt at a fixed ratio: 13.85 percent nitrogen by weight and 38.7 percent potassium, equivalent to 61.4 percent nitrate (NO3) and the same 38.7 percent K when measured as ions.

The Core Maths You Need

One gram of KNO3 dissolved in 100 litres of water raises NO3 by approximately 6.1 ppm and K by approximately 3.9 ppm. For a 60 litre tank wanting +5 ppm NO3 from a single dose, you need roughly 0.5 grams of salt. Most hobbyists premix a stock solution rather than weighing daily; a typical concentration is 50 grams of KNO3 in 500 ml of distilled or RO water, which gives 100 grams per litre stock.

Estimative Index Recipe for Singapore Tanks

The classic EI dose targets 20 to 30 ppm NO3 weekly through three or four doses, then a 50 percent water change resets the ceiling. For a 60 litre tank that translates to roughly 4 grams of KNO3 per week, split as 1 gram three times weekly, plus dosing on water-change day. From a 100 g/L stock that is 10 ml per dose. Pair this approach with the framework in our aquarium ei dosing complete guide for the full macro-micro schedule.

Lean Dosing Adjustments

Lean dosing aims for 5 to 10 ppm NO3 sustained, not the 30 ppm peaks of EI. For a 60 litre tank that means roughly 1.5 grams of KNO3 per week split across daily small doses. Carbon-limited and shrimp-keeping tanks suit lean targets because excess nitrate stresses sensitive Caridina. The lean dosing method planted tank guide covers the philosophy and the cross-checks against PPS-Pro and ADA approaches.

Mixing Stock Solution Properly

KNO3 dissolves cleanly in cold water but slowly. Use distilled or RO water, never PUB tap, because chloramines and trace minerals shorten shelf life and complicate the contribution calculation. Add the salt to half the target volume, stir until clear, then top up. Store in an opaque bottle out of sunlight; properly mixed KNO3 stock keeps for six months without degradation. Dispensing from a marked syringe avoids the 10 percent error that pouring from the bottleneck always introduces.

Where to Buy in Singapore

Food-grade KNO3 (saltpetre) is sold for curing meat at certain Tekka Centre spice shops at around $8 per kilogram. Aquarium-grade KNO3 is essentially the same compound but sold in 250 g aquarium pouches at C328 and Polyart for $12 to $15. Garden-supply potassium nitrate from horticultural shops works equally well at lower cost. Avoid lab-grade KNO3; the purity premium is wasted on plant tanks.

Symptoms of Over and Under-Dosing

Nitrogen deficiency shows as pale, yellowing older leaves and stunted new growth, especially in heavy stems like Rotala rotundifolia. Potassium deficiency shows as pinhole damage and ragged margins on older leaves. Excess KNO3 rarely harms plants but can fuel green-spot and green-dust algae, particularly when phosphate is low. Cross-reference our aquarium plant deficiency guide for visual identification of each symptom set.

Interaction With Phosphate Dosing

KNO3 should be balanced against KH2PO4 at roughly 10:1 NO3 to PO4 ratio for typical planted tanks. If you dose KNO3 alone without phosphate, plants quickly hit a phosphorus ceiling and the unused nitrate fuels algae. The aquarium phosphate management piece walks through the balanced approach.

Carbon Limitation Matters

Dosing KNO3 in a non-CO2 tank produces marginal benefit at best because plants cannot turn the nitrogen into biomass without carbon supply. In low-tech tanks, drop dose targets to 5 ppm NO3 sustained and rely more on fish waste. CO2-injected tanks at 25 to 30 ppm CO2 use KNO3 efficiently and reward the dosing investment. The aquarium co2 guide covers the carbon side of the equation.

Singapore Tap Water Considerations

PUB tap water is soft (GH 2 to 4) and chloramine-treated, which means baseline nitrate is essentially zero and your dosing maths starts clean. The soft water also limits how much KNO3 you can dose before TDS becomes a concern in shrimp tanks; 50 ppm TDS rise from heavy KNO3 dosing can stress sensitive Caridina. Monitor with a TDS meter weekly if you keep crystal red or wild-type shrimp.

Schedule for a 60 Litre Planted Tank

For a CO2-injected 60 litre tank with moderate stems, dose 1 gram of KNO3 (10 ml of 100 g/L stock) on Monday, Wednesday and Friday, plus 0.5 grams on water-change Sunday. That delivers roughly 21 ppm NO3 and 13 ppm K weekly before plant uptake. Adjust upwards if you see nitrogen deficiency, downwards if NO3 readings climb above 30 ppm at week’s end. Couple this with the routine in our aquarium water change guide for predictable parameters.

Related Reading

• Aquarium EI Dosing Complete Guide
• Lean Dosing Method Planted Tank
• Aquarium Nitrogen Dosing Guide
• Aquarium Potassium Dosing Guide
• Aquarium Dry Fertiliser Mixing Guide