There are a few potential causes for this. First, high levels of CO2 will cause precipitation of calcium carbonate. So, if you are dumping the kalk solution, it can incorporate CO2 into the mix, especially in a room with poor ventilation. Again, if your tank has high levels of CO2, it could potentially cause precipitation. Also low magnesium can cause precipitation of calcium carbonate. Magnesium competes for carbonate binding with calcium, so having low magnesium means more calcium binding. Calcium carbonate is less water soluble than magnesium carbonate, so a higher percentage of calcium carbonate to magnesium carbonate will show increased precipitation. Hope that is a little helpful. Alternatively, try using only 1/2tsp per gallon if your tank is not heavily stocked with calcium and carbonate depleting organisms.
|