Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Fish are best set up according to their GH preference.
Here is how I would handle your water(s):
1) If you want to keep fish that need soft water (low GH) then you will have to use the water with the lowest GH to start with, or else dilute the high GH water with reverse osmosis or distilled. Or find some way to remove the minerals from your tap water. Your tank, for whatever reason, seems to have the best GH for soft water fish. Please describe everything you are doing... SOMEthing is removing the minerals from your water.
2) Sodium exchange water softeners add sodium to the water and removes the calcium and magnesium that plants and fish need. This is not usually a good option for aquariums. I would not use softened water.
3) Well water has lots of minerals. Just keep the right fish:
Asian Rummynose, most Live bearers, many Rainbows and related fish (research Pseudomugil species), and Rift Lake Cichlids and other fish.
Here are some tests to run:
1) Run some tap water into a bucket. Try some softened water in one bucket, and well water in another.
2) Add a generous amount of peat moss to each bucket. Perhaps a cup of peat per gallon.
3) Stir the buckets as often as you can. Several times per day.
4) Test GH, KH and pH after 24 hours. If you have a TDS meter that would be great. (Can be found on line for about $20)
Other test: Put a nylon stocking of peat moss in the tank. In the filter, if you have room, otherwise in a place with high water flow. I cut a knee-hi into 3 bags for small tanks (to 20 gallon), or 2 bags for large tanks (to 45 gallon), and just use 1 bag for most of my tanks (2 bags for my tanks over 45 gallon).
Goal: See if peat moss will do the job for you. If this works, then you will have to prepare the water before every water change by filtering it through peat moss. I do this in garbage cans. I use a knee-hi stocking of peat moss in 20-40 gallons of water, and run a fountain pump to circulate the water overnight. The next day the water is ready. I can reuse the peat moss several times, but it takes longer each time. Keep the peat moss in a stocking, it can clog the pump if it is loose in the garbage can.
Get one of the substrates that removes the KH from the water. Oil Dry, Safe-T-Sorb, Turface (any color)
Put this material in a bucket the same as the peat moss test.
Test at 24 hours: Has the KH and pH dropped?
If both peat moss and Safe-T-Sorb do what they are supposed to, then test a combination. Put a cup of each in a gallon of water, and see what that does overnight.
If that works, then you have figured out what you will need to do to prep your water to keep soft water fish.
Fill a bucket or garbage can with water, and filter that water through Safe-T-Sorb and peat moss.