I’ve recently seen a freshwater tank that had red algae, but only thought that this could happen on saltwater tanks? Is it the same type of algae or was it not even algae and something else (similar to how black beard algae looks purple/like a black bush in freshwater).
Red algae is pretty rare in a freshwater tank, and is commonly found in saltwater tanks (think of it as their version of how common green algae is in freshwater tanks).
As far as it being the same - kind of, but not exactly. The one that grows in freshwater would never survive in saltwater, even though they have the same appearance it’s a different type of algae all together.