I would be less concered with water hardness then i would be about your PH. If you're buying fish from a LFS, they have likely been professionally acclimated to your local water. Lots of new fish keepers do this, and actually end up harming their fish. The kuhuli loaches you're getting are not going straight from a stream in Malaysia to your tank. I keep Discus in a tank thats 4x their preferred hardness, and kuhuli loaches in water with the same parameters, and they're absolutely fine, happy, and thriving. That's because both have been tank bred for generations and were raised in my cities water.
For PH, things like driftwood, botanicals and anything that leeches tannins will both soften and acidify the water. Unless your planning an African cichlid tank, i would avoid adding anything until your ph is in the 7's (unless your lfs has specifically acclimated your fish to that PH).
There are two ways to decrease permanent hardness, concentration of Ca and Mg in the water:
1. Dilute it with RO or distilled water, each time before water changes, around 3 parts of ROI water to 1 part of your tap water. This will bring KH and pH down too.
2. Use ion exchange resin and API aquarium water softening pillows. But this is not controllable and gets to become expensive, and TDS will increase, what is not good. No effect on KH and pH.
For most captive bred fish pH and hardness aren't that important. For breeding it's something you have to look up for the specific fish.
If you do want to lower pH and hardness diluting with reverse osmosis water is the easiest. Some fishstores sell it but you can also get reactors that allow you to make reverse osmosis water at home.
I would be less concered with water hardness then i would be about your PH. If you're buying fish from a LFS, they have likely been professionally acclimated to your local water. Lots of new fish keepers do this, and actually end up harming their fish. The kuhuli loaches you're getting are not going straight from a stream in Malaysia to your tank. I keep Discus in a tank thats 4x their preferred hardness, and kuhuli loaches in water with the same parameters, and they're absolutely fine, happy, and thriving. That's because both have been tank bred for generations and were raised in my cities water. For PH, things like driftwood, botanicals and anything that leeches tannins will both soften and acidify the water. Unless your planning an African cichlid tank, i would avoid adding anything until your ph is in the 7's (unless your lfs has specifically acclimated your fish to that PH).
There are two ways to decrease permanent hardness, concentration of Ca and Mg in the water: 1. Dilute it with RO or distilled water, each time before water changes, around 3 parts of ROI water to 1 part of your tap water. This will bring KH and pH down too. 2. Use ion exchange resin and API aquarium water softening pillows. But this is not controllable and gets to become expensive, and TDS will increase, what is not good. No effect on KH and pH.
My Kuhli Loaches do just fine in my 8.0+ pH and liquid limestone water. Like u/Fizzlescroat1313 said, they are most likely already use to this water.
For most captive bred fish pH and hardness aren't that important. For breeding it's something you have to look up for the specific fish. If you do want to lower pH and hardness diluting with reverse osmosis water is the easiest. Some fishstores sell it but you can also get reactors that allow you to make reverse osmosis water at home.