My flock has roundworms! To many for individual treatment!

[natyvidal]

So I went on a week long trip leaving my daughter in charge. According to her description she saw roundworms. I've read about them and individual treatment. Is there anything I can use in their water? And treat again in 7-10 days? If so, for how long should I put it in the water? And is there egg retrieval? Prefer to use a medicine without it. For long periods!
Thank you for your help.

 

[Eggcessive]

How many do you have? I have wormed a large flock individually before with Valbazen, and many use SafeGuard. Here is a product that can be used in the water for 2 days:
https://jedds.com/products/wormer-deluxe-powder-jedds