How long is concrete plug cure time ?

[SnoopDog]

I recently made some frag plugs with concrete and southdown and have a few questions. I used Portland cement #1 and standard southdown sand with a 2/3 ratio. The plugs are rather small, i used a 1 inch PVC cap as a mold and poked plastic dental picks through for something to pierce mushroom frags with.

1) What should they be cured in water or vinger ?
2) How long before they should be reef safe ?
3) Has anyone seen any ill effects of concrete plugs in a reef tank ?

 

[Anonymous]

Use plain water, no need for vinegar.

Rule of thumb is to soak them until you don't notice any significant pH "upping" due to the alk. in the concrete.