Item 8646 Your Price today: $ 3.74 Currently out of stock. Call or e-mail for availability info, or else click here for a form to tell us how many you wanted to order. Pro-V Betta Waste Absorbing Crystals are a decorative gravel media to be used in the Betta Bow-Front Tank Kit (item #8539) or in any goldfish bowl for natural ammonia absorption. Crystals are mixed blue and white. Recommended replacement is every 30 days. 5.5 oz container.