Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Have you looked up your water company's water quality report? Pretty much all of them seem to be on line. Some are more informative than others.
TDS is measured with a meter. I got one several years ago on line for about $20, including shipping.
Here is how I manage this:
A) Know what I am starting with: Test tap water parameters.
B) Know the goal: Good water for the fish will grow most plants. If the goal is to grow a specific plant that is very particular, then target that. I have several tanks, so I can have hard water fish and plants in some, and soft water fish and plants in another. Most plants don't care.
C) If the tap water already has too many minerals (too hard GH or KH, too high TDS) then blend reverse osmosis or distilled or rain with the tap water until these test results are in the right range. I happen to have pretty good tap water. If yours has something in it that makes it a problem you may have to do something different in this part, perhaps start with pure RO.
1) Set GH to suit the fish. Since I am starting with fairly soft GH, I add Seachem Equilibrium to set the GH for fish that prefer harder water.
2) Set the KH about equal to the GH. I use potassium bicarbonate, but sodium bicarbonate (baking soda) works just fine, too.
You may have to adjust the recipe- raising the KH generally will raise the pH. Most fish that thrive in hard water (high GH) also prefer higher pH, but research your fish. When in doubt test a batch and add small amounts and dissolve it well to see what effect it has. While pH is not as important as GH to the livestock, it should not be totally ignored. You do not control the pH directly, you alter the KH, and this controls the pH.
3) If it is a black water fish, filter the water through peat moss to add tannic acids.
Do not try to adjust the water after it is added to the tank. This would mean that every time you do a water change the fish are subjected to whatever it is you are removing from the water for however long it takes for the 'water softening pillow' to do its job.
Do whatever you need to outside the tank (I use Rubbermaid Brute garbage cans) so a water change means the water is already at the correct parameters when it enters the tank.