i know some people add hydrated lime, or calcium carbonate to their bulk substrates, ive even herd of oyster shell flour, i dont have any of this on hand, but i have diatematious earth whish is essentially million year old fossilized oyster shell four...does anyone have experience with this? if so how much do you use etc? it seems like it would work but i want to make sure before i use it in my sub, ....also has anyone used kelp meal? ive got a bit and was thinking of putting a bit of that in as well...

he,

i don't know about diatematious earth but my reason for adding lime or oyster shell is to prevent contams. The best pH of a substrate is 5.5 to 6.5, so you don't want to use lime in substrates. Use gypsum only, its not for adjusting pH. Gypsum is for adding calcium and sulfur, both aid in fruit-body development, and both are usually lacking in most substrates.
To prevent contams ad lime, soda or oyster shell to your casing layer the ph of 8 will help prevent most spores from germanating.

hope this helps

i would imagine DE is safe, and a cursory google seemed to validate that (As did the shroomery).

idk about kelp.

I throw in paramagnetic volcanic rock dust. I collect this volcanic rock around my area and powder it and add it to soils, mushroom substrates..w/e..

Works for me. Paramagnetism and diamagmetism are important aspects of soil health that are often missing these days.

DE is made of diatom frustules, these are made of silica, not calcium. It is not a bad thing to add to a substrate, but it cannot take the place of lime.
http://en.wikipedia.org/wiki/Frustule