Well no, you will not be able to determine at a KH of 0. pH test probes will also not work on pure water. You have some salts but no HCO3.
HCO3/CO2 is an acid base buffered system. Without the base, there's no pH/KH relationship.
The system will crash, it might not have done this yet for you, but you'll get burned at some point. And have dead fish.
My question to you is this: why do use RO water with no KH added back?
Bring it up to 2 at least.
Do this for your fish and for your plants. It will help and cause no issues with any fish or plants you mention or anyone's mentioned, even wild Rio Negro Discus, Altums etc do fine at a KH of 3.
Plants will use KH if there is not enough CO2 also. You may be hitting the right amount of CO2 for now, but that may not last long. If the plants do not have enough CO2 at some point, then the pH wioll rise dramatically since there's no base to balance it. Our blood has the same acid base system and is why we exhale CO2 as we oxidize the sugars we eat for energy.
Think about the acid base system, if you add a lot of acid and there's no base to balance it, then you can have very large pH fluctations. Potentially lethal to fish also.
Add some baking soda and raise the KH to 2-3 range, then add enough CO2 to get about 6.3-6.5 range.
All the fish will and can breed in this range.
Food and feeding will help the most in general with most breeding issues.
This will take care opf both fish and plants.
In general, taking care of the plants takes good care of the fish, the rest is mainly feeding.
Regards,
Tom Barr |