I have a small 108 gal. pond with 2 koi who winter in my classroom. I sat at the edge of pond with feet in H2O and bailed with to clean and there were these tan & brown things stuck on my feet, especially between toes! YUCK! I had to scrape them off with fingernails. At bottom of pond there were lots. Pet store man sold me Cupramine (?) and told me to dose at 5x recommended strength, wait 3 days, drain, refill, repeat, then fill and bring home fish & plants. The suckers were still doing fine! So I decided to pour in a lot of kosher salt (like Dead Sea). After 3 days I used hubby's shop vac to empty, (learning!) rinsed a few times and now refilled. No sign of life. Fish are coming home tomorrow. Were those leeches or anything that would harm the fish? Is there a better way to get rid of them? Pond store proprietors here would not give me answers even when I showed them bad video which I will try to share here. Ignore mosquito larvae,they are all dead from Bt. Look at stringy critters. Sorry this is so long.