High GH, but not enough Mg
Mg deficiency has shown up suddenly, I guess because the GH of my tap water has decreased slightly, but still fairly high at around 7 degrees. The water report says around 7 ppm of Mg, but apparently it's not quite adequate. 50% weekly changes should only be adding about 3.5 ppm.
This week I added Epsom salt, about 3-4 ppm worth, but how will this affect the GH? I don't want to increase hardness too much and I really don't want to purchase an RO unit unless it's absolutely necessary to get enough mg in the water. I have soft water fish- harlequin rasboras, neons, CPDs. My fish don't breed, except for I'm guessing the CPDs (I saw a single tiny fry once), but seem to be fine in my water and are otherwise very healthy and colorful.