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My Tank Thread
Most tanks don’t need additional potassium supplementation; water changes and foods usually supply enough for most tanks.
However, some folks note a higher demand for potassium, possibly from salt mixes, ionic imbalance from certain 2 parts, consumption, or even the types of foods being fed. Further dosing may be necessary in those tanks.
Potassium in natural seawater is about 400 mg/L or 400 ppm — I recommend maintaining that level. Not higher.
Extremely elevated potassium disrupts cellular ion balance in corals, causing osmotic stress. This can be very stressful, impair coral metabolism, and potentially cause death. Never shoot for high targets.
I do not recommend home kits for testing potassium, as they may be inaccurate or give false negatives, leading to very high levels after dosing.
The most reliable testing method is ICP-MS, followed by ICP-OES. Either of these tests works for determining if potassium supplementation is necessary for your aquarium.
What source of potassium should I dose?
Potassium chloride is the single best additive for increasing potassium without skewing ionic balance. If you want to be precise, a small amount of potassium sulfate would be even better, but it’s never necessary in this context.
Food-grade potassium chloride is ideal. Many sources contain trace amounts of magnesium hydroxide carbonate, which may slightly increase alkalinity, pH, and magnesium; it’s unlikely to ever be detectable in most cases.
Let’s get to the recipe:
Potassium chloride (KCl) is 52.4% potassium by weight.
To achieve 1 ppm of potassium (K) in 100 L, we need 100 mg of potassium.
Since potassium chloride is 52.4% potassium:
100 mg / .524 = 190.8 mg KCl needed.
To make the solution, dissolve 190.8 g of potassium chloride in 1 L of RO/DI or purified water.
1 mL of this solution will raise potassium by 1 ppm in 100 L.
However, some folks note a higher demand for potassium, possibly from salt mixes, ionic imbalance from certain 2 parts, consumption, or even the types of foods being fed. Further dosing may be necessary in those tanks.
Potassium in natural seawater is about 400 mg/L or 400 ppm — I recommend maintaining that level. Not higher.
Extremely elevated potassium disrupts cellular ion balance in corals, causing osmotic stress. This can be very stressful, impair coral metabolism, and potentially cause death. Never shoot for high targets.
I do not recommend home kits for testing potassium, as they may be inaccurate or give false negatives, leading to very high levels after dosing.
The most reliable testing method is ICP-MS, followed by ICP-OES. Either of these tests works for determining if potassium supplementation is necessary for your aquarium.
What source of potassium should I dose?
Potassium chloride is the single best additive for increasing potassium without skewing ionic balance. If you want to be precise, a small amount of potassium sulfate would be even better, but it’s never necessary in this context.
Food-grade potassium chloride is ideal. Many sources contain trace amounts of magnesium hydroxide carbonate, which may slightly increase alkalinity, pH, and magnesium; it’s unlikely to ever be detectable in most cases.
Let’s get to the recipe:
Potassium chloride (KCl) is 52.4% potassium by weight.
To achieve 1 ppm of potassium (K) in 100 L, we need 100 mg of potassium.
Since potassium chloride is 52.4% potassium:
100 mg / .524 = 190.8 mg KCl needed.
To make the solution, dissolve 190.8 g of potassium chloride in 1 L of RO/DI or purified water.
1 mL of this solution will raise potassium by 1 ppm in 100 L.
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