I am wanting to start supplementing my feed with kelp. The best bang for my buck is this... https://www.amazon.com/Dogzymes-Cer...=1491715887&sr=1-11&keywords=kelp+for+animals But, it has iron in it. I have read a lot about chickens not being able to have iron. So, can they have some, just not alot? Or what? What kind of kelp do you use? I am not spending a ton- but also dont want to make my girls sick.