Are your coral ugly? Do you have coral that are dying? Do you not know why? Maybe the silent killer is what’s missing! Potassium! Gardeners care about it. We are underwater gardeners. Why don’t we? Reef aquarists are keeping photosynthetic symbiotic animal gardens in their tanks. As important as potassium is for photosynthesis, it should be important to us in our aquarium maintenance regime. Along with all the other “iums” there are in the coral keeping vernacular, one that should also be in conversation is potassium. Why are we forgetting this critical element? There is as much potassium in the ocean as there is calcium. Potassium is a critical element in fertilizers. Phosphorous (in the form of Phosphates in aquaria) and Nitrogen (in the form of Nitrate in aquaria) are the other elements that are listed in the ever present NPK rating. It is important that the ratio is correct in the fertilizer, so as to best grow your crop. Potassium is considered a macronutrient, along with nitrogen and phosphorous, as well as familiar elements to reefers, calcium, and magnesium. Another macronutrient that is a not as familiar: sulfur. In Australia fertilizers are rated with an NPKS ratio. Maybe we need to look there for some more clues in the future. Seawater usually contains about 400 ppm potassium. Not far off from the 420ppm for calcium. It is a regular practice of reef aquarists to keep higher calcium levels in their aquariums to support stony coral growth. Also most home aquariums have higher nitrate and phosphate levels than what is found on coral reefs in the ocean. In keeping with regular aquarium husbandry techniques, and being mindful of maintaining a proper balance of the major NPK nutrients in our tank, many aquaria may benefit from controlled potassium dosing.
Goniopora benefit from higher Potassium as well as Iron and Manganese levels.
I only feel comfortable now encouraging the use of potassium chloride, after half a decade of using it myself on various aquaculture and display systems. I have found it safe if used properly and I depend on it to keep my corals vibrant and healthy. More and more people are trying potassium chloride dosing, so hit them up and find out what their experience has been.
Fungia and their relatives exhibit excellent growth and vivid coral with higher Potassium