Hi all,
I also don't think tap water will contain large amounts of it, ours (Bath) certainly doesn't. There isn't a regulatory limit for the K content of drinking water in the UK, so you would have to request the value from your water supplier. As a ball park figure rivers in the UK generally contains about 2-3 ppm potassium, and our tap water (from a limestone aquifer) less than 1ppm. If you live in an area with a lot of granite, particularly if it is partially de-composed (China clay mining areas), or where the water quality is fairly iffy anyway (East Anglia, major conurbations) you might get a bit more in your water, but my suspicion would be that plant growth would be K limited in nearly all UK tap water.
cheers Darrel
I'm not sure why Tropica don't add K (potassium), but plants need large amounts of it. If you are growing hydroponic Lettuce, Tomatoes etc. you need growing solutions with about 300 - 500ppm K, compared to 200 - 300 ppm N and about 35ppm P. On a dry matter basis plants are on average 2% - 3% K. Potassium is necessary for the synthesis of proteins, and in the osmotic regulation of stomatal opening, amongst other functions.My slant on adding K, is that it stimulates photosynthesis, and that it is not a macro element, but more an essential element like Co2 is to plants. There is the argument that K is never really needed in an aquarium as our tap water usually has enough.
I also don't think tap water will contain large amounts of it, ours (Bath) certainly doesn't. There isn't a regulatory limit for the K content of drinking water in the UK, so you would have to request the value from your water supplier. As a ball park figure rivers in the UK generally contains about 2-3 ppm potassium, and our tap water (from a limestone aquifer) less than 1ppm. If you live in an area with a lot of granite, particularly if it is partially de-composed (China clay mining areas), or where the water quality is fairly iffy anyway (East Anglia, major conurbations) you might get a bit more in your water, but my suspicion would be that plant growth would be K limited in nearly all UK tap water.
cheers Darrel