Oyster Shell (Crushed) 15lb. Bag by Coastal Oyster shell provides a long-lasting, steady release of nutrients to help regulate pH levels, improve fertilizer uptake, promote healthy cellular structure and enhance soil tilth Oyster shell is also helpful in creating more active habitats for soil microbes in compost piles and worm bins Promotes strong eggshells pullet size crushed oyster shell 5 lb provides a good source of calcium that builds strong eggshells for your birds. heat-treated for purity. contains pullet-sized crushed oyster shell and coral calcium. use as a calcium source to promote strong eggshells.