Quick reference
Aquarium fertilizer calculator by tank size
EI doses for common US tank sizes, computed from molar masses. Pick your size for lean EI, low-tech, stock solutions and liquid product doses, or use the full calculator for any volume in liters, US or UK gallons.
EI dry doses per dose (3× a week)
| Tank | Liters | KNO₃ | KH₂PO₄ | K₂SO₄ | CSM+B | Seachem Flourish (label) |
|---|---|---|---|---|---|---|
| 10 US gal | 38 L | 0.463 g (463 mg) | 0.054 g (54.2 mg) | 0.41 g (410 mg) | 0.116 g (116 mg) | 0.8 mL |
| 20 US gal | 76 L | 0.926 g (926 mg) | 0.108 g (108 mg) | 0.82 g (820 mg) | 0.232 g (232 mg) | 1.5 mL |
| 29 US gal | 110 L | 1.34 g | 0.157 g (157 mg) | 1.19 g | 0.336 g (336 mg) | 2.2 mL |
| 40 US gal | 151 L | 1.85 g | 0.217 g (217 mg) | 1.64 g | 0.464 g (464 mg) | 3 mL |
| 55 US gal | 208 L | 2.55 g | 0.298 g (298 mg) | 2.25 g | 0.638 g (638 mg) | 4.2 mL |
| 75 US gal | 284 L | 3.47 g | 0.407 g (407 mg) | 3.07 g | 0.87 g (870 mg) | 5.7 mL |
| 125 US gal | 473 L | 5.79 g | 0.678 g (678 mg) | 5.12 g | 1.45 g | 9.5 mL |
EI weekly targets: NO₃ 22.5, PO₄ 3, K 30, Mg 6, Fe 0.6 ppm, split into three doses with a 50 % weekly water change. Full nominal volume, no substrate allowance. UK gallons are 20 % larger than US gallons, so use the calculator in UK gallons if your tank is sold in imperial gallons.