Wazine is marketed for chickens... it's best to use FIRST if you haven't dewormed the chicken before and it may have a heavy infestation. It ONLY kills round worms, but in a heavy infestation, there can be a lot of round worms, so you don't want to overload the system with tons of dying worms all at once.
Then, in approx 10 days to 2 weeks, use something a little stronger. I'd suggest one of the paste dewormers marketed for horses, like Zimectrin Gold. (gets everything plus tapeworms) There are others that target tapeworms, too... well, one other... Equimax, I think. Just look at the box and make sure it says it gets TAPEWORMS, too. Give just a pea sized amount orally. I just dose it out onto my finger then scrap it into their beak, but some put it on a piece of bread and feed each bird a piece. Save the rest (lots!) for when it's time to deworm the flock again. There's a very wide margin of safety on this med... don't panic if you give a little too much. (it's something like 20 X's or higher is the 'overdose' level at least-- and even then, death isn't the likely outcome)
To my knowledge, only Wazine is labeled for poultry in the US...everything else we use for chickens if 'off label' use, marketed for other animals.
Wazine is dosed into the water.