These good fresh water quality filtration blocks break down bad waste keeping your aquatic friends safe. There are many porous pores in the middle of the water quality filtering medium, which can help provide a environment, reducing the content of nitrates in water, and promote more healthy water quality. Features - Color: Yellow. - Material: quartz sand. - Size: About 16.00X3.70X3.70cm/6.29X1.45X1.45inch. - The square filter material the space of the filter tank and arrange it more neatly. - The whole body has many , which can quickly decompose the nitrite load caused by fish feed. - Strong adsorption capacity, can absorb 80% of harmful substances, promote fish metabolism and excrete bad substances in the body. - Increase the amount of dissolved oxygen and remove heavy in water. - Purify the water more effectively and maintain the balanced in the aquarium. Package list: 4 tank filter supplies