I think you'll want it in the late 5s for best nutrient availability. Especially iron. I managed to do that when feeding lots of gas but I'm looking for alternative ways to keep pH low. Unfortunately I don't have a pH meter anymore but I suspect my ph is still in the 7s-late 6s.
My tank is becoming more of a test tank by the day. I've removed the charcoal which may have been adsorbing heavy metals. I was using it for tannins. I added too much zinc yesterday after a weighing error. Fish seem ok but could be a time thing. Diatoms are on the decline.
I think I'm going to have to have 5 bottles with individual metal concentrations in to enable trouble shooting. I really want to get this pH down too. KH test kit says I'm at 9 but this is supposedly very soft water. I suspect there's lots of chemicals in the tap that are manipulating the water to be artificially maintained at a desirable set of parameters. Rainwater is becoming more appealing by the day.
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