EISCO 12PK Raw Gray Limestone, Sedimentary Rock Specimens - Approx. 1" - Geologist Selected & Hand Processed - Great for Science Classrooms - Class Pack

For use in the classroom my students struggled to compare basalt and this limestone because it was so dark. It was only density that helped them distinguish between the two. Pieces are about 1" each.

Small but looks nice in my 10 gallon tank. Kind of expensive for the size. Baught it to try to bring up my ph in the tank. To soon to tell if it worked.

I would give it a 5 but they're very small for how much they are. I've been keeping freshwater shrimp and snails for 10 years now. Snails and shrimp NEED calcium and the best way to give that to them long term is limestone. Sadly, I live in an area where I cant easily find limestone. If you have limestone in your driveway or in your yard, I recommend rinsing that off and using that instead.

This product arrived early and was exactly as described.