I have a 75 gallon tank with a yellow tang, psudochromis, green chromis, starfish, shrimp, crabs, and snails. I noticed red spots growing on my sand. I also have bubble algae and purple algae on the rocks. The bubble algae came on the rocks but is now spreading. What am I doing wrong? Is the red algae harmful? What should I do to get rid of the red algae and bubble algae? Thanks for any help!