Dry vs liquid fertilizers: which should you use?
Dry salts are cheap and flexible. Commercial liquids are convenient and pre-balanced. Both deliver the same ions; the difference is cost, control and convenience.
Three ways to fertilize
- Dry dosing: weigh powder (KNO₃, KH₂PO₄, K₂SO₄, MgSO₄, CSM+B) and add it straight to the tank. Cheapest and most flexible; needs a scale accurate to 0.01 g for small tanks.
- Home-made stock solutions: dissolve salts in a bottle once, then pour a fixed mL per dose. Same cost as dry, easier daily dosing, better for small tanks. How to make one.
- Commercial liquids: ready to use and often shrimp-tested, but you pay mostly for water and packaging, and they are usually much leaner than EI.
Side by side
| Dry salts | Commercial liquid | |
|---|---|---|
| Cost per year | Very low | Higher, rises with tank size |
| Control over N, P, K separately | Full | Depends on the product line |
| Accuracy in nano tanks | Needs a stock solution | Easy (mL) |
| Labeling | You label bottles yourself | Maker's directions |
Comparing them fairly
Convert everything to ppm. For example, Seachem states that 5 mL of Flourish Potassium in 125 L raises potassium by 1.66 mg/L, while 1 g of K₂SO₄ in 125 L adds about 3.6 ppm K. Tropica gives its Specialised Nutrition analysis as % by weight (N 1.3 %, K 1.0 % and so on), which we convert assuming 1 mL weighs about 1 g. The product library does these conversions and lets you mix products.
Mixing approaches
Many keepers dose dry macros and use a commercial trace product for micros. Just count each element once, and keep iron and phosphate doses on different days.
Open the dosing calculatorMore guides
Sources
- Seachem Flourish Potassium: concentration and dose
- Tropica Specialised Nutrition: declaration and dose
- Tropica Premium Nutrition
- Potassium sulfate: composition
Written in our own words from the sources above. Numbers are educational starting points; check product labels and your water.