I've just set up my new tank (48hrs test run - no fish yet) and my latest check-up shows that everything is fine...except the KH level. I used spring water to fill up the tank so the water is extremely soft and my KH level is at or near zero. Now I need to raise the KH to an acceptable level of 4 - 8 KH. Any suggestions (add baking soda, tap water) etc? Anyone else face this start-up issue? Also, is it advisable to keep using spring water or opt for tap water? Thanks.