Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Yes, IMO those are pretty low.
Here is how I handle that problem.
1) My tap water also comes out of the tap with a high pH (highest 7s to low 8s mostly), but GH and KH are usually about 4-5 degrees, though they dropped to about 3 degrees this summer.
2) Most of my fish are fine with that, but I do have a Lake Tanganyikan tank, and some livebearers that prefer harder water.
3) Most of my tanks have substrates that remove the KH from the water and this allows the pH to drop to 'off the chart low'.
Set up the tank (set up 1 or 2) with water that is prepared with extra minerals. I use baking soda for KH and Seachem Equilibrium or Barr's GH Booster for GH.
1 teaspoon of baking soda per 30 gallons of water will raise the KH by 2 German degrees of hardness.
If you do not want to add sodium to your tanks then you can use potassium bicarbonate to add carbonates.
GH Boosters will have on the label the dosing. Make the water suit the fish.
For soft water fish I do not add any minerals, but you might want to keep the GH and KH about 3 German degrees of hardness, to be sure there are enough minerals for plants and fish. The nitrifying bacteria use carbonates, and some plants can get carbon from carbonates.
Through the week the substrates that remove the KH (set up 3) can work so fast that I need to add more. I just sprinkle the baking soda into the tank where the filter flow is the strongest, and most of it dissolves before it hits the bottom. Over the years these substrates finally quit, and the tank holds stable through the week. The newer ones sure gobble it up, though.
I also keep coral sand and oyster shell grit in the filters of the hard water tanks (1 and 2). I use nylon stockings as media bags. These materials dissolve too slowly to use during water changes, but are good through the week to add just a trace of minerals as might be used by the plants. Keeps the GH and KH right where I want it. (unless the substrate steals the KH).