SeaChem Gray Coast™ Calcite in FW tank?
 

I'm kinda confused, the description say marine or tropical tanks, I did a little research and some say it's ok for FW, some say it's not. Just wanted to get an opinion. Here is the breakdown:

http://i91.photobucket.com/albums/k2.../GrayCoast.jpg

The plan is, I have a 22 pound bag left over from my SW tank. I was thinking about mixing this in with the 40 pounds of Tahitian Moon sand I just ordered. It is for my 75g planted community tank. Thoughts?

Hmm.. I'm not entirely sure this would have any use really. If your tap water PH is low and you're trying to raise something like livebearers perhaps.

This is calcareous [the list of ingredients has calcium and magnesium, the two prime minerals of harder water], meaning it will likely raise hardness and pH or at best keep them where they are; it says it will prevent pH decline, so it must release some mineral hardness. In a livebearer or rift lake cichlid tank, this would be fine, especially as ladayen says if you had soft water to start with. I have a gravel very similar to this in my 20g which has Emerald Dwarf Rasbora that require some hardness and a basic pH, and my tap water is very soft, so this works well. I would not use it in any aquarium with soft water fish.

Byron.

Yeah...not trying to use if for any special reason other than I have it on hand and it would act as a filler so I don't have to spend a crap load more money on more black sand for my tank. The pH of my water is about 7.6 but no idea the hardness. I'll have to get that checked next time I'm at the LFS...I don't have the test kit for that. But if it isn't a good idea...I guess I'll chuck it.

Yeah, unless you have a specific reason for using it, it will only limit your options. With your PH already at 7.6 raising it anymore would cut your options quite a bit.