Easy kalk question

[gnesh69]

Can someone remind me why I can not add Kalk directly into my 5 Gallon tank of top-off water?

[bertoni]

I add kalk to my topoff water regularly. Kalk can spike the tank's pH, though, so tuning the amount of kalk per gallon takes some experimentation. This article might help:

http://reefkeeping.com/issues/2005-01/rhf/index.htm

[Randy Holmes-Farley]

I also add it to my 88 gallon top off reservoir. They critical point, however, is that it must be added very slowly, such as dropwise, otherwise the ph spike that Jonathan mentions is too much. Adding 1.25% of the tank volume of limewater to your tank will instantly boost pH by about 0.6 pH units, which is too much unless the tank pH is very low (below 7.9, IMO).