Controling KH, GH, and Ph for cories and ember tetras

My tap water sits at around 6.8-7 ph, Gh of 150-180, and Kh of 40ish. Now both my Gh and KH are drastically out of range for the fish I'm planning for (pygmy cories and ember tetras), my PH is fine and stable so I don't want to mess with it. The tank is a 20 gal (75 liters) for referenece.
I obviously need to lower it and by a lot, Both GH and KH need to be lowered to around 10. At the moment I'm working on my GH with an api water softening pillow, not sure if you guys find this effective but it seems to be helping. Tannins seems like the best way to lower the KH but it sounds like they also lower PH and make it unstable. Thoughts on tannins for the KH?
I do hear a lot that as long as GH/KH are stable they're fine out of range and most care articles don't even care to mention either parameters, but mine are so out of range so I'm not sure how important it is for me to change them. Am I worrying over something that's not even that vital?
Thanks for the help and sorry for the beginner questions

 

I think your existing parameters are fine for pygmys and embers. I’d leave it as is and give them stable conditions. They are both fairly adaptable species too.

 

You're worried about nothing because the range you are reading is in degrees, and you are reporting in ppm.

GH @ 150-180ppm = 10 degrees.
KH @ 10ppm <<< 10 degrees.
KH @ 10ppm matches the pH reading you are reporting.

Your numbers are perfectly fine for those fish. No need to change a thing.

 

Your KH is fine: 40mg/l (= ppm) equal about 2.5 degree. Which is acceptable for both species. The GH, equaling about 8°, is also fine. Both down to 10mg/l would mean you'd have to use 1:9 ratio of tap to RO. For that you can go with pure RO immediately. Both species would be ok with that, but necessary... it is not.

 

You're worried about nothing because the range you are reading is in degrees, and you are reporting in ppm.

GH @ 150-180ppm = 10 degrees.
KH @ 10ppm <<< 10 degrees.
KH @ 10ppm matches the pH reading you are reporting.

Your numbers are perfectly fine for those fish. No need to change a thing.

I'm an idiot apparently, glad I can finally get fish soon. Thanks!