Reply From Sea Chem:
Borate has two primary advantages. 1)Borate is a source of buffering
alkalinity that unlike carbonates/bicarbonates will not be rapidly
removed through routes unrelated to buffering. Carbonate loss occurs
through biological utilization (and atmospheric equilibration to a
lesser extent) in addition to the loss that normally occurs through
its contributino to buffering. None of this is "bad", this is simply
how carbonates are supposed to function, but in a closed system like
an aquarium there is a greater risk of reaching a dangerously low
level of buffering capacity (as opposed to an open system like the
ocean). Borate alkalinity provides that "safety net", so even if all
of the carbonate alkalinity were depleted, there would still be
borate alkalinity functioning to prevent a disaster.
The second advantage in a reef system is that borate is involved in
competitive ion pairing with calcium. This has an overall net effect
of increasing the calcium stability in the system in comparison to a
system that had 0 borate and had 100% carbonate alkalinity. This
helps prevent precipitative loss of calcium as calcium carbonate as
well as allowing one to maintain a higher level of calcium (if they
so desire, i.e. one can go higher with less risk of calcium carbonate
precipitative loss).
:happyfish
