I am currently in the process of treating my tank with de wormer. I originally did this because I saw hydra in my tank after adding plants and so far the treatment has killed all of them. Then I found these flat white worms and doing some research I was hoping that they were planaria but it has currently been 6 days since I have treated the tank and they are still alive. I was supposed to do the first water change today but I have put it on hold because of the worms. What worms are these if not planaria?