Diy frag plugs

[chewie]

You will have to let them sit in water, changed out often, for a while to get the ph of them to come down to 8 or so. I made a batch of diy rock a few years ago using cement, crushed oyster shell and argonite (sp..?) sand. Took about 8 months of them in rubbermaid containers with downspout running into them for the ph to go from off the scales 12+ to around 8.5..
Im sure a few off them in your tank would not affect your tanks ph not sure how it would affect what your trying to frag on them, if you dont cure them.
I have read some people putting theirs in a mesh bag in back off toilet to cure.