william

Mostly they speared everywhere, is there any place where they don't grow ? They can't grow in a sterile environment unless introduced. Once there are enough nutrients available for growth they will grow

I see, what makes them fastest growing ? Not sure, but they can be spread by rain and dust particles, likely they were in a cyst state during this process.

It was probably due to the interparticulate interchange between the air and water surface that algae get up in the air.

Amano shrimp perhaps? They're pretty cool and do a decent amount of tank clean up for the small bio load they create