Gh,kh low in rainwater planted discus/ community tank

[Gwokky]

Hello guys, I’m trying to get a plan for setting up co2.
the pH is 6, gh 5, kh 0, no ammonia, no nitrite, nitrate around 20ppm and the gh is pretty much all from equilibrium as I have live plants.
The rainwater being obviously soft and mineral/salts void, my main concern is ph swings due to lacking kh. Although my discus seem to do really well, I’ve struggled with anubias and certain other plants, but also don’t want to bump carbonate too much to keep the fish happy….???
I have seachem ferts but want to do away with excel and go the bubble.
my idea is to run a plant substrate ( maybe fluorite or tropica) in media bags buried under the gravel so I can still vacuum and was also looking at onyx sand to mix into my existing gravel.
would this be a wise plan to gently raise kh for both the flora and fauna? And would it help with th ph swing control due to co2 ???
any advice on co2, ph and hardness would be awesome please!!!

[Tech Support AN]

Thanks for the post, Gwokky!

I think adding in the Onyx Sand would be a great idea since you have zero KH and plan to add CO2 injection. This will serve as a safety net for pH by slowly releasing carbonates into the water. Another option would be to use our Acid and Alkaline Buffers to target a specific KH and pH. If you email us at [email protected], we can provide you with a helpful calculator for using those buffers in a planted aquarium.