Making
SW rock out of concrete has been around for a long time, at least as far back as I began with SW tanks, 1986. Check the web site reefs.org, i would think that there would be articles from people who have done this sucessfully. Cement cures in water or air - doesn't make a difference to concrete, however, if you place in the tank your
pH and KH and other values will spike upward and remain there until the rock is cured. Here is what i remember:
Do not use ordinary gravel that is contained in post mixes which may have heavy metals that could dissolve more readily in saltwater.
Use sand and gravel like crushed coral, aragonite sand, dolomite, crushed oyster shell or builders #20 white silica sand (which may contribute slightly to higher silicate levels)
New cement rocks will leach heavy amounts of
calcium oxide and calcium hydroxide which is the same as
kalkwasser. You need to cure these rocks for at least 8 weeks. If you add these newly made rocks, your pH, KH and other values will harm or most likely kill your fish. Cure the rock in large buckets so that you can put in a water pump or something to move water around the rock. Second add an airstone and CO2 if you can (use
DIY CO2 system) (CO2 combines with the KW to make calcium carbonate) and speed up the curing - but only somewhat. Change the water at least once a week. After approx. 6 weeks check your pH and KH vlaues about once a week, once your pH i below the value of your tap water and stays their - should be good to go.
The larger rocks will cure much slower than the smaller rocks (duh)
I seem to recall that hard water or regular tap water with a higher pH than
RO water due to minerals in hard water.
Check web sites for live rock cement and do alot of reserch on curing so you can get a good concensus on what people have done with curing that suceeds. And of course the more time curing/leaching of minerals the better.
Hope this helps.
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