What Kind Of Rock

[darkwolf29a]

As Andy said...Just cure it and it'll be fine.

As for rocks I normally use in a freshwater aquarium...I'll use just about anything. Right now, I have some slate and some granite in my tanks.

As for bricks...I'd use them, but only after they'd sat in water for a few weeks, to make sure that any chemicals they might have come into contact with have been removed. Honestly, bricks are no different than terracotta pots. All that stuff is based on clay, and then colored and such to get the end result the manufacturer wants. Nothing to worry about with brick.

 

[andywg]

If you really want to be more careful about pulling imperfections out of materials which will dissolve in water, consider a few RO baths. If it won't come out into RO, then it isn't that likely to come out into tank water either.

Even after curing cement et al I expect that there will still be slow dissolving and leeching with regards to pH, but it will be at a level that regular water changes will more than take care of.