bethany
Most natually occuring live rock ( not aquacultured rock ) is made up of dead coral skeletons.
This stuff was once a living coral, and colonies of these corals make up the reef itself.
Some of the reef breaks off - someone collects it - and we buy it as live rock.
It should be very porous - and it is very brittle indeed.
You can often crush it in your hands or break bits off as you move it and stack it.
These skeletons ( live rock ) are made up of CaCO3 - calcium carbonate. This calcium carbonate was formed by the LIVING CORAL years and years ago. The living coral secreted this stuff to make it's inner structure or skeleton. It was a hard coral.
( as the reef is weathered and pounded by the tides and currents, the reef coral calcium carbonate breaks off, is eroded into smaller bits and tiny pieces - and eventually after many many years - it becomes aragonite sand )
The ROCK itself is dead now. The bacteria, coralline algae, pods, worms and other critters is what makes it alive or LIVE.
So .... being that the actual rock is dead - it does not need calcium to "make it strong" as your LFS person said.
It's rock - not a living bone.
Coraline algae needs calcium and carbonates to grow. Now this stuff is certainly alive - and as it grows on the live rock - it may have a tendency to make the outer layers of the live rock stronger, but not the internal rock itself. If anything, the inner calcium carbonate rock will dissolve over time. It's dead.
If you do decide to add calcium to promote coralline growth, and for the general health of the saltwater chemistry and tank critters - I would encourage you to also maintain your alkalinity and monitor pH.
When we talk about adding calcium to a tank ..... the very first thing that should pop in our heads is;
What will this do to my alkalinity
What will this do to my pH
What will this do to my calcium
Dosing one without monitoring and adjusting/maintaining the others - can lead to some serious problems.
But ..... making the live rock stronger is not necessarily one of them.
