I rescued two bull frogs from my biology lab earlier this year and I just discovered that they may have parasites. However, I have never seen the parasites in their tank before until now. The only difference that I have changed in their environment was to feed them crickets. Since the new cricket diet I have noticed but only once that there were parasites in their habitat. After I stopped feeding them the crickets I have not seen the worms. I know that parasites can still be in their digestive tract. Do I need to take them to a veterinarian or can I purchase de-wormer over the counter?