Fish use corals for food and shelter. And finally, corals are very old and they grow extremely slowly. If a big coral head that has a size of around 3 feet dies it will take more than 100 years to replace it. On the top of the pipes we put plastic tubes which trap falling mud. We change them every second week.
Some pipes are longer than others.
This is because I want to collect different kinds of sediment. If mud particles fall on coral reefs, they do not disappear. They will just be moved from one place to another by the currents and wave action. After changing the tubes, I filter the water that got collected in them. I dry the filter with the sediment particles on it and weigh them.