My water source is from a well with relatively Low GH (3-4) and very high kH (160-180 range). My pH is around 8.2. I am installing a R/O unit and this is my first experience with one. Its my understanding that the R/O will remove all kH. What will it do to pH? I would like to re-constitute/buffer the water that is held in my reservoir to get back to a pH around 6.8-7.2 and average kH (whatever that # is). What products or methods would you recommend? And is there some interaction with CO2 that can bounce pH around during this process? Thanks for your input.
Water chemistry experts needed:
- Thread starter Erik333
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Pure water is ph 7, and your RO unit should produce water that is close to that. Enough so that you will have to add minerals back depending on what your fish's needs are. Unless you are adding CO2 there is not that much effect from that source.
In an established planted tank though there are both inorganic influences on ph, the KH reading for example, and organic ones that you can't test for. The way to know how much the CO2 you are adding is changing the ph is to take a sample of the tank water and put it in an open container to reach equilibrium with atmospheric CO2. The difference in ph from tank water to sample is then isolated to CO2 caused. 1 Log ph difference is about 30 ppm CO2, so if your tank reads 6.5 and the sample reads 7.5 then you have enough CO2, or tank 7.0 and sample 8.0 etc.
In an established planted tank though there are both inorganic influences on ph, the KH reading for example, and organic ones that you can't test for. The way to know how much the CO2 you are adding is changing the ph is to take a sample of the tank water and put it in an open container to reach equilibrium with atmospheric CO2. The difference in ph from tank water to sample is then isolated to CO2 caused. 1 Log ph difference is about 30 ppm CO2, so if your tank reads 6.5 and the sample reads 7.5 then you have enough CO2, or tank 7.0 and sample 8.0 etc.
If you are interested in CO2, research threads on Drop Checkers.
That 30PPM rule falls apart if there is enough buffering capacity in your water to maintain a given pH despite addition of a fair amount of CO2. The method prescribed above is less than reliable. A drop checker, some 4dKH solution and bromothymol blue (found in most test kits' pH indicator bottles) are are the way to go.
SnakeIce - thanks...i'm not quite sure I understand what you are saying, but i'll re-read it. I guess to rephrase my question...if my R/O water comes out at 0 kH and 7.0 pH, what do you all recommend to keep the water stable because I believe at 0 kH, the pH could bounce around quite a bit?
Well one method is to use the RO water to cut the source water's Total Dissolved Solids (TDS) down to an acceptable level for what you are trying to do by adding a portion of source water back in. You would have some buffering that way and still have the benefits of water that isn't as hard as your source. The down side is that you don't know what is in the water.
The other option is to buy something to add to the RO water. Kent R/O Right is one product that comes to mind. There might be other brands but that is what I remember.
The other option is to buy something to add to the RO water. Kent R/O Right is one product that comes to mind. There might be other brands but that is what I remember.
