From Kent's website:
Directions: Dissolve one teaspoon of Superbuffer-dKH in a glass of fresh water. Add directly to tank or sump for each 20-30 gallons (80 liters) of tank capacity each day until the desired pH and alkalinity (carbonate hardness or KH) are reached. Wait 1 hour to remeasure alkalinity, but wait 24 hours for pH to stabilize, before re-measuring (full pH increase and stabilization may take up to 48 hours!). This product is designed for reefs and may be used in fish only marine systems also.