The tabs release the CO2 in the water and thus stimulate the growth. Healthy plants can absorb many times more of this important nutrient, Co2, as is available in the air. Adding Co2 short before the dark period doesn't give any results, as the plant doesn't absorb Co2 in the dark! The tabs bond the Co2 about 4 to 6 hours to the offered water.
Use: Dissolves within 90 seconds at normal water temperature. Active for 48 hours after dissolving. Does not affect the EC value. Store in a dry and cool place. Improper use will not be reimbursed.