Concrete brick

Did anyone try concrete brick for cave/s? I have some good results, try for some time to make caves with coconuts, flower pots etc.
http://www21.zippyshare.com/v/21360538/file.html

Bricks are so heavy, and you must have some big aquariums. One thing I don't know is how do they effect in water parametars? I add some water from RO, i don't have tests for water hardness, don't know if concrete increase gH.

my advice is to take it out asap!

Cement leaches all sorts of horrible stuff into water and takes years and years before it is safe. It will jack you KH and your GH and may cause other issues too.

It's too late now, male guarding eggs, we will see what's happend