using hydraulic cement for stacking rock

[tmz]

TMZ you're scarin me!
Are these concerns with the additives that make the hydrolic type set up faster, or are you talking cement generally? If the whole point of the expensive hydrolic stuff is that it sets fast under water, it seems pointless to risk it if you are going to cure it out of the tank before hand...

Also, fwiw my big public aquarium (Boston) is a joke reef-wise. They just have some sad Xenia and anemones and stuff. Most of the customers want to see big fish and pet sharks, those tanks are all fake plastic coral, I don't think they give a lot of thought to aluminum or whatev.

As I understand it hdyraulic cement replaces some of the cement around 20% IIRC with the aluminates to allow it to set in water . The aluminates may take insoluble forms after curing; I'm not sure since they may react to acids in the tank at some level.

Portland cement,non hydrolic , doesn't use aluminates. It relies on CO2 and the evaporation of the water.
Both will influence pH and may contain levels of other impurities. Both are alkaline and exothrmic( give off heat during curing) and can be caustic during the curing reactions.

 

[CStrickland]

Cool, thanks