Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

These will form all sort of fungus and mold, but only when running for longer periods like yours there, and never gets the chance to dry out inbetween use.
Mine is about a decade old now, and still delivers completely clean water in itīs collector, but that also only see occasional use, if i (or someone in "the circle") needs to dry out new concrete floors or similar when restoring/rebuilding.