I have been feeding a small amount of microworms once daily in my 10 gallon Dwarf Cory tank at work off and on in an attempt to get them to breed for a couple months now. I went on vacation from two weeks ago and left pre-measured flake food for a coworker to feed while I was gone. When I returned to work I noticed one of my adult shrimp was dead and there were small white palm tree looking growths on the glass of the tank. I did some research and determined that it was Hydra. They had to be young because none were over an eight of an inch, fortunately. I found the below You Tube video that suggested that Hydra could be treated by using canine dewormer. I followed her instructions to the letter and as she said, three days later there were no more hydra and no fish or shrimp fatalities. I did a water change yesterday. When I came it today there are at least four of the tiniest shrimp I have ever witnessed so it must not have had any terrible effects on them.