How to prevent ph swings?

[Ice Man]

I got 25 gallon planted tropical community tank with DIY co2 setup. My problem are ph swings. Everything was OK as long as I used hard tap water, but since switching to RO water I noticed ph dropping to 6.6 from 7.4. I am using Natural Regulator and R/O right to treat water.
I heard people mix RO water with regular tap water. I did that for first few weeks/PWC, but not I am using just RO water with R/O right to keep kh at around 7.
BTW, co2 is always disconnected for night.

 

[DirtyTankMan]

You could run an airstone as well as disconnecting

 

[Rivercats]

Just curious but why are you using RO water? Is you tap water super hard with a high ph? Our tap water is GH13, KH11, PH9 which was not suitable for my mainly south american fish. I had to use straight RO until I got my numbers down to where I wanted them. Now I monitor my reading and use RO as needed to keep numbers at desired reading. I've never used any of the products to add back into RO water so I am no help there... sorry.
When are you taking you ph readings? They will be lower after the CO2 is running a bit but during the night they should rebound up, have you ever taken a morning ph reading before the lights and CO2 are turned on? You might find you have a different reading. I have a friend who uses CO2 and that is info I have gleened from him. Hopefully someone who uses CO2 can chime in and give you more insight.

 

[ejaramillo01]

I got 25 gallon planted tropical community tank with DIY co2 setup. My problem are ph swings. Everything was OK as long as I used hard tap water, but since switching to RO water I noticed ph dropping to 6.6 from 7.4. I am using Natural Regulator and R/O right to treat water.
I heard people mix RO water with regular tap water. I did that for first few weeks/PWC, but not I am using just RO water with R/O right to keep kh at around 7.
BTW, co2 is always disconnected for night.

IME, the pH swing is not as important as some people believe. In other words, fish can tolerate the pH changes just fine.
Once we introduce CO2 to a tank, the pH will drop, and every time that we do a partial water change, the ph will swing.... This happens on most of the planted tanks, and I have never experienced problems with the fish.

But I also agreed with the previous post, hard water will help you as a buffer to reduce the pH changes.

 

[CorallineAlgae]

There are situations with tap water, other than KH or GH, that make using RO necessary.

The post above is right. You should always expect a pH drop when you use CO2. The drop you're seeing is actually normal and still in the safe range. I wouldn't advocate using Neutral Regulator though. It would help us if you could tell us why you decided to go with straight RO. I have terrible tap water and mix RO with it to keep my pH stable. You may have a good reason abandon tap but it's usually better, and easier, to amend RO with at least some tap instead of using pH regulators.

 

[Ice Man]

My tap water is high in nitrates, around 40 ppm. That's why I use RO.

 

[BillD]

Some may disagree with this but if I had a planted tank, as opposed to a tank with some plants, I would be happy to use that 40ppm tap water.As far as the pH swing, yours sounds more like a shift, but either way it isn't a concern, if the basic water parameters are staying the same. If you are using CO2, a pH swing is normal, as mentioned.

 

[CorallineAlgae]

My tap water is high in nitrates, around 40 ppm. That's why I use RO.

Good reason. Ouch! You know... Amazon has pH balancing post RO filters for about $20 shipped. The one I looked at uses calcite to bring the pH of RO water back to neutral. I use a similar one for my drinking and sometimes even tank water. They're just for making RO water healthier to drink (not acidic) but the tiny amount of added minerals "may" make it a little bit more suitable for freshwater tanks than straight RO.

Even with your nitrates it's still good to use at least some tap water in your mix for water changes. May seem like odd advice but having the minerals from even bad water is still better than using pure RO. Just my opinion though.

 

[aqua_chem]

The pH swings caused by CO2 are pretty much entirely a non-issue.

 

[Ice Man]

Thank you all for your advices. I measured ph this morning and it was 7.4
I think I am going to mix 50% tap water with 50% RO water and see what happens.

 

[rkilling1]

Some may disagree with this but if I had a planted tank, as opposed to a tank with some plants, I would be happy to use that 40ppm tap water.As far as the pH swing, yours sounds more like a shift, but either way it isn't a concern, if the basic water parameters are staying the same. If you are using CO2, a pH swing is normal, as mentioned.

I agree with Bill. I normally add enough NO3 to be at least in the 20's. It is not uncommon to have my NO3's in the 40's.

The only issue with that is if you keep shrimp. Shrimp will not tolerate that high of NO3's.

 

[ejaramillo01]

I agree with Bill. I normally add enough NO3 to be at least in the 20's. It is not uncommon to have my NO3's in the 40's.

The only issue with that is if you keep shrimp. Shrimp will not tolerate that high of NO3's.

I did not know that about shrimp....I have. 10 G red cherry shrimp tank, which runs around 30 to 40 ppm of Nitrates. Looks like my shrimp just keep reproducing.
Lol