Hi, welcome to BYC!
I would NEVER take chicken advice from that well meaning friend, EVER!
Are you kidding me?! Most people who live in the city already have chlorine in their tap water. Anything that will kill the bad stuff will also kill the good stuff.
Ways to keep internal parasite down would be not overcrowding your flock, don't do things to attract wild birds to your yard, maintain good cleanliness in your coop. and don't feed directly on the ground.
I personally don't randomly worm because what a waste of time, A) if you don't have worms in the first place. B) if you don't end up treating for the correct worms. C) worms build resistance to the medications.
If you suspect you have worms (only roundworms can been seen in droppings), it is worth it to have a fecal float done at the vet. usually around $15. They will do a count which includes species so you can be sure and treat for the right thing, or maybe not treat if it isn't needed!
Many people will claim they treat with things like DE and "don't have worms." But
NONE I have seen have done a single float test before OR after to see if they even had worms and then to see if their (truly ineffective) method had the desired effect in their SUPPOSED worms. Some climates simply have less issues than others. In 6 years, I haven't had to treat for worms yet. Partly because I didn't know you needed to way back when. But currently because I don't have any symptoms that warrant it. I did buy a microscope to do my own floats, but with it being so easy to count bubbles thinking they are eggs with the home method.. I plan to just have the vet do a float annually (not sure what time of year I will choose), and I will try and do my own with the same sample so I can compare my amateur results.
Though NO worm load would be ideal.. there is often some worm load. But there is a threshold for when treatment is needed, according to the count.
Best wishes!