[Plinkploop]

Does it smell really bad? It's a stupid question but cyano typically has a very nasty fishy smell. There are some sheet algae that aren't cyano that act like this that you can remove and it smells more earthy than fishy, those can typically be handled with manual removal and ample water changes- also adding circulation to your tank can alleviate some of these algae issues. I hope this helps.

 

[Plinkploop]

Earthy is usually sheet algae 😁👍 that stuff is really ugly but can be dealt with by manual removal and the addition of proper ratio ferts. My experience with sheet algae has been very good with proper tank and filter maintenance and manual removal. I wish you luck!!