How to Mix Dry Fertiliser for Your Planted Aquarium

Commercial liquid fertilisers are convenient, but once you are running multiple planted tanks, the cost adds up fast. Mixing your own solutions from dry fertiliser mixing planted aquarium salts slashes that expense by up to 90% while giving you full control over nutrient ratios. This guide from Gensou Aquascaping at 5 Everton Park, Singapore, covers the essential compounds, recipes, safety considerations and dosing methods you need to get started. With over 20 years of experience maintaining planted aquascapes, we can confirm that dry dosing is one of the most impactful upgrades a serious hobbyist can make.

Why Mix Your Own

A 500 ml bottle of branded liquid fertiliser costs $15-$25 in Singapore and lasts a few months on a single tank. The same money buys enough dry potassium nitrate to dose a 200-litre tank for several years. Beyond cost, dry mixing lets you tailor nutrient ratios to your specific plant species and water conditions. Running a high-light CO2-injected tank that burns through iron? You can boost iron independently without raising everything else. That precision is impossible with off-the-shelf all-in-one liquids.

Essential Dry Compounds

You need just a handful of chemicals to cover all macronutrient and micronutrient needs. For macros: potassium nitrate (KNO3) provides nitrogen and potassium, monopotassium phosphate (KH2PO4) supplies phosphorus, and potassium sulphate (K2SO4) adds extra potassium if needed. For micros: a pre-mixed trace element blend such as CSM+B or Plantex is the simplest option — it contains iron, manganese, boron, zinc, copper and molybdenum in balanced proportions. All of these compounds are available from chemical suppliers on Shopee and Lazada for $5-$15 per 500 g bag.

Equipment Needed

Invest in a digital scale accurate to 0.01 g — these cost $10-$20 on Lazada. You also need clean, food-grade bottles (500 ml or 1 litre), a measuring spoon set, distilled or RO water for mixing and a permanent marker for labelling. Keep all chemicals stored in a dry, cool location away from children and pets. While aquarium fertiliser salts are low-toxicity, they should still be handled with basic care — wash hands after mixing and avoid inhaling powder dust.

Standard Macro Solution Recipe

For a 500 ml macro stock solution targeting a modified EI (Estimative Index) dosing regime: dissolve 30 g KNO3 and 5 g KH2PO4 in 500 ml of distilled water. Shake well until fully dissolved — warming the water slightly speeds this up. Each 10 ml of this solution dosed into a 100-litre tank adds approximately 5 ppm NO3 and 1 ppm PO4. Dose three times per week on alternate days from your micro solution. Adjust quantities up or down based on your tank’s plant mass and light intensity.

Standard Micro Solution Recipe

Dissolve 15 g of CSM+B trace mix in 500 ml of distilled water. Add 1 ml of hydrochloric acid or a few drops of a chelation acid to prevent precipitation and extend shelf life. Each 10 ml dosed into a 100-litre tank provides approximately 0.1 ppm iron along with balanced traces. Dose three times per week on days alternating with your macro doses. Store the micro solution in a dark bottle or cupboard, as light degrades the chelated iron over time. Replace the solution every four to six weeks for maximum effectiveness.

Dosing Schedule

A typical EI-based weekly schedule looks like this: Monday macro, Tuesday micro, Wednesday macro, Thursday micro, Friday macro, Saturday micro, Sunday 50% water change. The large weekly water change resets any nutrient accumulation and prevents toxicity. Some growers prefer leaner dosing — halving the EI amounts — for tanks with moderate light and slower-growing species. Track your results over four to six weeks and adjust gradually. Consistency matters more than perfection when it comes to dry fertiliser mixing planted aquarium routines.

Safety and Storage

Label every bottle clearly with its contents and concentration. Never reuse old food or drink containers without thorough cleaning and permanent labelling — the risk of accidental ingestion is real in a household. Store dry compounds in sealed, moisture-proof bags or containers. KNO3 is an oxidiser and should be kept away from heat sources and flammable materials. In Singapore’s humid climate, moisture can clump powders and degrade micro solutions faster — store supplies in an air-conditioned room or sealed box with silica gel packets.

Troubleshooting

Cloudy stock solution indicates undissolved salts — add more water or warm the mix gently. If plants show iron deficiency (pale new growth) despite dosing, your micro solution may have degraded — mix a fresh batch. Algae outbreaks after switching to dry dosing usually mean the balance is off; reduce light intensity temporarily and verify your dosing calculations. Use an online aquarium fertiliser calculator to double-check your numbers before committing to a recipe. With care and attention, dry dosing delivers professional results at a fraction of the retail cost.

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