Dr Tim's Aquatics Time-Release Waste-Away Gels maintain tank cleanliness by releasing beneficial bacteria that securely bind and break down organic waste. The gel can last up to 30 days and appears gray when it needs to be replaced. To use, unzip the wrapper, remove the tab, and attach the suction cup (included), then attach the gel inside the tank or filter box, avoiding direct water flow. For deep cleaning, use Waste-Away Liquid first, followed by the gel to maintain cleanliness. Make sure to use the appropriate size gel for the tank, and do not add other bacteria, amino acids, fertilizers, sugars, or vitamins within 48 hours of placement. If the water becomes hazy after a big cleaning, remove the gel and store in a sealed plastic bag in a dark, cool place. A biofilm may form on the gel, but this is normal and can be wiped off with a paper towel if desired.