Another way you can lower PH (and much more effective) is using seltzer water. I always keep a liter of Sam's Choice Sodium Free Seltzer water around. Preferably you want something with just water and carbon dioxide. I don't have a formula for how much to add, but it will bring the PH down very rapidly, so you'll want to add it slowly. Generally, you'll see the results within 30 seconds or less.
How are you adding your kalkwasser? Hopefully, you were dripping it as I advised. Did something happen to make it start dripping faster? I once accidentally added about a half gallon of kalkwasser, thinking it was plain water, and I had pretty much the same thing happen, except my PH shot up to over 9. There didn't seem to be any lasting damage, so I think you're tank will be fine as well. Anyway, let us know exactly what happened, and hopefully we can prevent it from happening again.
How are you adding your kalkwasser? Hopefully, you were dripping it as I advised. Did something happen to make it start dripping faster? I once accidentally added about a half gallon of kalkwasser, thinking it was plain water, and I had pretty much the same thing happen, except my PH shot up to over 9. There didn't seem to be any lasting damage, so I think you're tank will be fine as well. Anyway, let us know exactly what happened, and hopefully we can prevent it from happening again.