just moved into this house two weeks ago, managed to bring all my water and everything from my 75 gallon marine tank to the new house and it was time for a water change last week. i tested my tap water and everything was great! nitrates were even 0. so i was down in the basement doing wash and i saw some sort of ultraviolet sterilization filter built into the home plumbing. i want to take a picture to see if someone can identify if this is something that is like a RO/DI filter and will give me the best possible water for my aquarium. but anyone ever see some sort of filtration like this that isnt RO/DI? i think i have a copper test but i couldnt find it after i moved. i will have to dig around more. what does everyone think?