UGH!! I was cleaning out my water fall (the water pools in several spots when waterfall is turned off). I have not had my waterfalls going b/c we have been doing construction and I did not want to deal with high PH, etc... So I started to dump the water out as it was gross and I noticed these red stringy things. I thought maybe it was bird poop since birds love to hang out on my falls. So after I got as much as I could out, I decided to pour in some bleach to kill off the yucky stuff. All of a sudden these little red things came to life wiggling around. GROSS. What are they, where did they come from and how do I get rid of them?