Glossary · 🌿 Plants & algae
Biofilm
Biofilm is the thin, natural layer of micro-organisms that grows on surfaces in a maturing tank; it is a food source for shrimp, snails, fry and grazers like otocinclus, and a sign of a healthy establishing ecosystem.
A little biofilm (and a bit of algae) is not dirt to be scrubbed away — it is part of why a mature tank supports delicate grazers that starve in a sterile new one.
This is why fish like otocinclus and animals like shrimp do best added to an established, "seasoned" tank rather than a brand-new one.