I have these bug looking things on all my glass. They seem to only be on parts of glass that I missed when scraping algae. So I assume they are not harmful as I think they are probably consuming the algae. I did have 3 of my fish get what looked like brook just after I noticed these creatures. Unfortunately the fish died before I could do anything about it. I dont think that these things were what killed my fish. But im unsure. Please help!!