@AddictiveAdam, tap water has a lot of nutrients and contaminants in it. My tap water read 256 ppm
total dissolved solids where as my RO
water reads 0 ppm
. The extra stuff in the water can lead to algae outbreaks and be harmful or irritative to your tank inhabitants.
With that being said, I just mixed up 18 gallons of tap water with salt to do my water change tomorrow. It's necessary. I've had >1 ppm
ammonia along with high nitrates after my huge cyano
die off. I just didn't want to mention it publicly ;p