Domestic Oyster Shells 500g x 2 (1kg total) High-temperature heat-treated oyster shells. Releases minerals and calcium. Absorbs chlorine and ammonia, which are harmful to fish, and maintains pH when setting up a tank or changing water. Decomposes components that cause cloudiness and odor in the aquarium water, providing powerful purification. ● How to Use ・ Rinse lightly before use. ・ Place this product in a filter media net and set it in an external filter or top filter. (Effective if placed in an area with water flow in a top filter ◎) ・ Use approximately 300g for a 60cm aquarium. ・ After about 3 months, the surface of the oyster shells will become dirty, and the filtration effect will diminish. ・ Replace when you feel the effect has decreased. ● We also accept bulk purchases and requests for large quantities. Please write the desired quantity in the comments. (Price will vary due to shipping costs)