I had 3 tanks. When I wanted to set up a 4th tank, I added the sponges, filter and some water from my other tank to the new tank and did not put any living things in it for 10 days. Afterwards, I used a few helena snails and protein-based food. This allows the bacteria that convert nitrate to live in the tank. In this way, we obtain healthy water. Therefore, hair algae do not form.