Yes, there are specific expiry dates depending on the product. Check the back of the label for the best before date.

When dosing alkalinity supplements, you must be aware of your tank’s calcium level. If your calcium level is too high or low in relation to the alkalinity level, you will create precipitation, which can look like cloudy water. When dosing alkalinity, always consider the net volume of your tank. With larger quantities of live rock, deduct 20% of the aquarium volume when dosing alkalinity as a starting point, then adjust by testing and verifying the resulting KH value.