sambo said:I used the same basic "five parts aggregate to one part cement, but used as aggregate..
1 part aragonite sand (Seflor Special Grade?)
1 part crushed coral
3 parts crushed oyster shell.
Crushed oyster shell's dirt cheap at most farm supply stores. Used for chicken feed supplement, or something.
We also used the "feed store" oyster shell. Never again! We have so many algea blooms and have narrowed it down to the rock leaching phosphate and organics. I have doubts that the feed is pure crushed oyster shell.