Crushed Medium Pieces - Crushed medium grade pieces approx 15mm-25mm - This is an alternative to the full size shell, but in a crushed format, giving large surface areas of contact to the water flow.

Crushed Medium Pieces - Crushed medium grade pieces approx 15mm-25mm - This is an alternative to the full size shell, but in a crushed format, giving large surface areas of contact to the water flow. Supplied in a 20kg plastic bag. These are genuine Pacific Oyster shells and are a superb method to buffer and maintain a constant pH to your Koi pond. Filter media bags are available to retain the shell, which can then be ready for total immersion into the filter. This is exactly the same media that 9 out of 10 Japanese breeders keep in their filtration systems.