Planted Tank Guru
Join Date: Apr 2011
Location: Hamilton, Ontario, Canada
It should stay, and if you top off, only top off with RO, or in your case, your tap water should be enough. lol. Then when you water change, make your 5 gal jug or whatever you use to the same kH as the tank and you should be good. It gets disolved in the water and doesn't really come out.
If you don't change or top off water for a while, then adjust your kH water accordingly.
Say you don't do much to your tanks for 2 weeks and in 2 weeks, 10% of your water has evaporated. Then your water will be 10% roughly higher in kH, that's why top off's are important, usually with RO if possible. It keeps all the minerals in the water the same.
20g platy, , 2 x 10g shrimp, 3 x 20g shrimp, 7.5g shrimp and 1 great dane/mastiff puppy.
Sump Pimp #2
My Tanks and my shrimps