Originally Posted by micheljq
Hello, I will try to answer. If I am mistaken please correct me.
Not sure there is a proper GH, depends on what kind of plants you have. Some will grow better in soft water, some will prefer hard water.
As for me, my tap water is soft (GH of 2-3). I have 2 little calcareaous rocks in my 65G tank, that make the GH go higher (now it is at 6), for 2 reasons.
If the GH is not too soft (at least 3), there should be enough calcium and magnesium in the water for most plants, it is commonly belived.
If the GH is not too soft, the risk of pH fluctuations is less risky.
Forgive my english, it is not my native language.
KH determines the buffering capabilities of the ph not GH. But everything else seems right. You also may want harder water if you have snails or other inverts because they need more calcium for their shells.
I wish I lived where there was soft water. Just moved and my gh is 17 out of the tap and kh is 13. Waiting on RO water is a pain.