Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
1 German degree of hardness at any one time, and you could raise it that much a couple of times per week.
This is a VERY conservative idea, based on fish a lot more delicate than Platies. Safe.
I never worried about the amount of K that is added with Equilibrium, and I went ahead and dosed w/ K2SO4 as well. K is one of the things that aquariums can handle a lot more of just fine.
However, if you are worried that the GH booster is not the right balance of Ca, Mg or that it might add too much K, then you can add Ca and Mg without the K in forms such as Calcium chloride, Epsom Salt (Mg), or add things to the filter that dissolve slowly such as coral sand, oyster shell grit or limestone sand or fine gravel.
For my Lake Tanganyikan tanks I used a combination approach: New water for water changes was prepped with Equilibrium, and the substrate is coral sand, in there is oystershell grit in the filter. Lots of snail shells too (shell dwellers), but I do not know how much Ca or Mg that provides. Water is so hard and alkaline they do not dissolve.
Platies are one of the live bearers that have been bred in captivity for so long that they are adaptable to a very wide range of water conditions. GH of 6 degrees is just fine. They are OK with GH much higher, too.