The first pic looks like hair algae. And yes its bad I had a round of it and i added a lot of extra flow that got red of it. If your nutrients/phosphates or high that will cause it. RODI water and light feeding your fish will help Also old lighting has been Sade to contribute to it
Thea will eat it but not likely Thea can keep up with it with out finding the cause.
you mite list your equipment and water supply -fish-feeding habits
whit do you have for water movement
I have a 950gph pump out of 2 outputs for flow. I feed the 2 damsels & 1 chromie frozen brine shrimp ( I also have 25 hermit crabs) once a day. I run a wet/dry dump set up.
You can add some power heads to get your water movement up id try for at least 30 times tank volume I have over 40 in a mixed tank with a deep sand bed and wont more
Your pump is probable only given you 60 to 75% of the rating
Snails wouldn't hurt. Just watch out your hermits don't go around killing them for their shells.
I had some hair algea growing in my tank for a while (I liked the way it looked) but I was gone for a weekend and they didn't get feed and when I came back it all was gone. So their may be a chance with swithing to everyother day feedings your fish will get rid of it themselves, and never miss a meal!