First test your tap water. alright. people are going to disagree with me here. However, i think it depends on your tap water. I have well water which is not treated by anything (chlorine). Having tested my tapwater for phosphates and nitrates (testing was acceptable), I had been using aquasafe (very small amt) to reduce metals (incase they were in the well/pipes). However, i have recently just started using straight well water without adding aquasafe because it might have phosphates in it. I switched to the chemipure filter media which reduces metals. WHENEVER possible, i do buy gallons or RO water, but i have to drive an hour and a half to get it! so it is not often that i am able to use it. I also have chaeto algae. I think you just need to know your tap water, and i would definitely be very leary of town tap water, because it is always treated with something that could be harmful.