My RO water is 5.5 out of the tap and I reminerlize with Salty Shrimp Mineral GH/KH+ and my ph around is 5.9 and it drops to 5.3 with the co2. Is this low ph bad for the fish and plants? I have plenty of GH and a slight kh reading.
1) 75 Gallon
2) GH is 75ppm KH is 2
3) Loaches, hill stream loaches and tetras. Swords, Cryps and Vallisneria
4) Fluval Plant and Shrimp Stratum
Had the tank running for a 2 weeks and it seems ok. I calibrated my ph sensor and was surprised at how low the ph was. The tank is a rebuild of my old 75 gallon. I used a little of the old substrate and same canister filter so cycling isn't a problem. I dose EI with co2 injection. I use Salty Shrimp Mineral GH/KH+ to reminerlize the water.
It isn't a bad idea to raise the KH a bit with baking soda. But, the effect is to raise the pH a bit, not to increase the pH stability of the tank. KH does not stabilize the pH, once it is above zero - let's say 1 to be sure it isn't zero. Once the KH is that high the pH changes will be the same as when it is 10. I know this is counter to everything we read about KH, but it is still true.
Another reason to have a higher KH is that some plants can use carbonates as a source of carbon, driving the KH down a bit. Obviously that would be a bigger problem if the KH is very low, than if it is above 4 KH, for example.