I think you will find that things like coral will have little or no effect in water that has an alkaline pH. A buffer, while it may affect pH, is not the same as a pH "up" product. As an example, baking soda, will raise pH some, but has an upper limit. It is generally used as a buffer, as compared to a strong alkaline such as sodium hydroxide, which will raise the pH drastically. This is much like the way an acid will lower pH, but in reverse. It is important to understand the way a buffer works and it's purpose, which is to keep pH stable. Basically an alkaline buffer, such as baking soda will absorb any added acid, until it (the buffer) is consumed, at which point the pH will drop. This is how one keeps a swimming pool at the correct pH, and the principle is the same in aquariums.
