Aquarium Salt Calculator
Aquarium salt grams from tank volume and ppt with change recharge.
What it does
Aquarium salt steadies freshwater fish through stress and ich at 1 to 3 parts per thousand: grams equal ppt times liters, and only changed water gets re-dosed since salt never evaporates. Sensitive species and plants set the ceiling.
The tool above takes tank volume with target ppt and change percent. It returns initial grams with recharge grams and spoon estimates.
The default 40 liters at 2 ppt needs 80 g with 20 g per 25% change. A 20 liter tank at 3 ppt needs 60 g.
Dosing follows UF IFAS ich guidance with SRAC publications behind them. Both agree on 2 to 3 ppt and change-only recharge used here.
How to use
- Pick gallons or liters.
- Enter tank volume.
- Enter target ppt.
- Enter change percent.
- Read initial grams first.
- Recharge changes only.
Formula
- liters
- Tank volume in liters.
- ppt
- Target parts per thousand.
- change %
- Changed fraction per service.
- 19 g
- Coarse grain grams per Tbsp.
Gallons convert first (x 3.78541), then identical math runs. Salt never evaporates, so top-offs skip dosing. Most freshwater fish hold 5 ppt for weeks; plants often fail first.
Worked example
Example: 40 liter tank at 2 ppt
Imperial defaults: 10.57 gallons at 2 ppt, 25% changes.
- Tank: 10.57 gal = 40.0 liters.
- Target: 2 ppt stress and ich support.
- Initial: 2 x 40 = 80 g.
- Spoons: 80 / 19 = 4.2 Tbsp, weigh it.
- Change: 25% of 40 = 10 L holds 20 g.
- Recharge: 20 g premixed per change.
- Tool shows 80 g salt, 20 g per 25% change.
Reference table
| Use | ppt | Note |
|---|---|---|
| Transport calm | 0.1 to 0.3 | Mucus support |
| Stress and ich | 1 to 3 | Tank standard |
| Short baths | 4 to 5 | Species checked |
| Seawater ref | 30 | Ceiling context |
Limits
- Species limits rule; tetras suffer.
- Plants often fail first.
- Ponds impractical to salt.
- Estimates, observe stock.
Common mistakes
- Dosing top-off water.
- Spoon-guessing small tanks.
- Adding salt dry to tanks.
- Skipping dissolve and aeration.
- Holding sensitive fish at 5 ppt.
Try it yourself
Quick checks. Answers sit tucked under each question.
40 liters at 2 ppt?
2 x 40 = 80 g initial (metric mirror).
20 liters at 3 ppt?
3 x 20 = 60 g initial.
50% change on 40 L at 2 ppt?
2 x 40 x 0.5 = 40 g premixed per 50% change.
Questions
How is salt dosed?
Grams = ppt x liters. A 40 L tank at 2 ppt needs 80 g dissolved first.
Do water changes re-dose?
Only replacement water at target ppt: 2 x changed liters. Top-offs for evaporation get none.
What ppt treats ich?
1 to 3 ppt for stress and ich support; 4 to 5 ppt short baths where species allow.
Are some fish salt-sensitive?
Yes: tetras, electric fish, and live plants suffer first. Reduce and flush on stress signs.
Must I weigh salt?
Yes: spoons vary by grain, so scales rule and volume estimates follow.
Can ponds be salted?
No: ponds make ppt dosing impractical, so treat in tanks instead.