The Seaweed Infusion

This is an interesting method to introduce spores and micro elements to your tank. Just collect dried seaweed from any beach. Of course traces of other organisms are included, too. Keep it cool and dry. From time to time take a tiny portion, add some water from the tank and keep it in a cool and dark place for a day or two. After that add the "infusion" to your tank. New plants and may be other forms of life will show up.

Anyway, it is a way to add some "biology" to your tank, especially if you're far from the sea and can't add very often natural seawater...