Where you hate beating around the bush. People hate people being harsh even more. Take that into consideration if you are at all considerate. Now to your concern about these white hair like looking things. There will be a lot of guess work, because you don't know, the picture is bad, and you choose not to post numbers. Turn your blues off and take a picture for starts. It is an ID thread. Kind of hard to ID something if it is next to impossible with the picture you have taken. It's kind of like beating around the bush if you can't produce a good picture.
Do you carbon dose with vodka or something like that, because it could be a bacteria. People like to know numbers and dosing of things to see if it gives us any clues to your issue. If it is a sponge dying or alive, worm, feather duster esk like critter, bacteria, anemone, snail, barnacle shrimp, or other guess work listed. You will get exactly that till you choose otherwise.