Water parameter questions.

[Hf21]

Hi all,
I have posted on here before about mixing 50/50 ro to tap water. However when I do this my kh is like 1 so I have to buffer it. When I buffer it to 4 it then takes my ph back up to 7.6 and my gh to 12. My standard tap water is ph 7.8 kh4 gh 19. I want to achieve softer water pref around ph 6.8 kg anything around 4 or just over and a gh under 10 as I keep lots of Cory's but I know they like softer water and also wanting to breed them this year so want to achieve a more natural water for them. If I was to use pure ro water how to I re mineralise to achieve the required values above as when I buy to water it comes at a ph of 7 to start with so when re mineralising to achieve kh values by the time I'm done the ph is back up to high 7 and gh back up to about 13. I dont get how people achieve it with ro water.

 

[Byron]

First, mixing RO water and tap water is proportional. A 50/50 mix should reduce the GH by half, and the KH similarly. The pH will lower but this will be dependent upon the GH/KH and initial pH, along with CO2 so it is hard to say until it happens, but it should be fine.

Do not add buffering substances. First, the soft water species do not need this as they can manage with fairly acidic pH levels, so let the pH do what it wants. Second, it will be much more stable than messing around with buffers which only complicates the chemistry.

One (of many) myths in this hobby is the unfounded need to "buffer" pH. That is important in tanks with fish requiring moderately hard water with a basic (above 7.0) pH if the GH/KH are not sufficient to retain a basic pH. But in tanks with soft water fish, it is not necessary. These fish occur in habitat waters have zero GH and KH, and a pH on the acidic side (below 7), sometimes as low as in the 4's.

 

[Hf21]

First, mixing RO water and tap water is proportional. A 50/50 mix should reduce the GH by half, and the KH similarly. The pH will lower but this will be dependent upon the GH/KH and initial pH, along with CO2 so it is hard to say until it happens, but it should be fine.

Do not add buffering substances. First, the soft water species do not need this as they can manage with fairly acidic pH levels, so let the pH do what it wants. Second, it will be much more stable than messing around with buffers which only complicates the chemistry.

One (of many) myths in this hobby is the unfounded need to "buffer" pH. That is important in tanks with fish requiring moderately hard water with a basic (above 7.0) pH if the GH/KH are not sufficient to retain a basic pH. But in tanks with soft water fish, it is not necessary. These fish occur in habitat waters have zero GH and KH, and a pH on the acidic side (below 7), sometimes as low as in the 4's.

Would zero kh in an aquarium not cause the ph to be really unstable? In the wild there is alot more water than in the aquarium so it's like a constant water change. In the aquarium you would surely either have to do alot of water changes or it would become unstable?

 

[seangee]

I have 2 tanks with zero KH. Both of these tanks have an absolutely stable pH. One is heavily stocked with a lot of wood and plants and the pH is always around 5.6. The other has less fish, less plants and less wood and remains constant at around 6.2. Both of these tanks get a 75% water change every week, using identical water. I don't put anything else in the water - since I use RO I don't even need dechlorinator.

 

[Byron]

Would zero kh in an aquarium not cause the ph to be really unstable? In the wild there is alot more water than in the aquarium so it's like a constant water change. In the aquarium you would surely either have to do alot of water changes or it would become unstable?

I have had the same experiences here as seangee. Any aquarium will establish a stable biological system provided it is left alone; the aquarists who have the most difficulty with fluctuating parameters are inevitably the ones using substances to adjust the parameters/chemistry, and this creates instability. The only intervention should be regular substantial water changes. I have been changing 60-70% of the tanks' volume every week for more than 20 years. [And there are reasons beyond the GH/pH to be doing this that I won't get into.] I tested for pH and nitrate every week just prior to the water change, for about a year, then I tested periodically (maybe every four or five weeks), and also mid-week now and then. I kept records (one always should) and over a space of some four or five years, the pH never once varied in any of the tanks by more than one or maybe two decimal points [example, 6.2 to 6.4] from week to week., nor did nitrate. The latter was/is in the 0-5 ppm range, and pH is different in each tank but the tank with a pH of 6.4 remained at 6.4 over the several yearts, and the tank with pH below 5 [I assume, test only goes to 5) remained the same, and the tank with pH of 6 remained the same, and so forth. This is stability.

This works for soft water species, which is all I have because my tap water is zero GH/KH. I add nothing to any of the tanks to increase this, except the plant fertilizer but there is so little hard minerals in this that the plants use them long before they can ever show up in tests.

Hard water species like livebearers obviously need a much higher GH/KH and pH above 7. Depending upon the source water, adjustments may or may not have to be made.