Questions about new CO2

I've started my planted tank, and I want to maintain a pH of 7.0 as a happy place for all my flora and fauna. Currently there is no fauna.

I have a pH controller, which I haven't been keen on using, but allowing it to control the airstones does keep me right around 7.0.

Here's the situation:

• with just water and hardscape, my pH was 7.6
• after adding my first round of plants, it dropped to about 6.4
• the pH controller got it back up to 7.0
• Unfortunately, my CO2 drop indicator shows blue
• The CO2 started this morning, and pH quickly dropped to 6.3
• The pH controller and airstones couldn't counteract that, so I turned it off getting me back up to 7.0

Thoughts:

• I've ordered a GH/KH test kit, so I'll have that soon to measure. I'm on municipal water, so I would think my KH would be "normal".
• I've also read that having a 1.0 pH drop caused by injected CO2 should mean there's about 30ppm and would be a good target

So, my question: can I use an alkaline buffer to raise my existing pH to 8.0, and then use the injected CO2 to get it to my target 7.0?

 

It’s never going to stay at a set ph. You may want to consider instead turning the co2 down a little. I have co2 on a timer to come on an hour before lights come up and off an hour before lights go down. This is a long read but has good info. pH of Water - Environmental Measurement Systems

 

I failed to mention that I'm injecting CO2 at 1 bubble per second. I'm not sure how to go lower without shutting it off.

 

What is the kH of the tank?

Ideally:

If using CO2, ensure CO2 is dropping the pH of the tank water a full 1.0 – 1.2. To do this, measure the pH of tank water with no CO2 dissolved in it, and then measure again 2-3 hours after CO2 has been running. Ensure the drop in pH is a full 1.0-1.2. If the drop is not there yet, slowly up CO2 over a few weeks until at least a 1.0 drop is achieved, and watch fish / livestock carefully. Adjust CO2 down if you notice fish gasping at the surface and consider running an airstone at night when pushing a 1.2 or greater drop. For example, a tank water pH of 7.5 with no CO2 dissolved in it, should reach a pH of 6.5 – 6.3 for CO2 to really shine, and for maximum plant health.

Consistency in CO2 levels is key to plant health. Keep CO2 levels as stable as possible once a desirable level has been reached.

 

If 6.5-6.3 is an ideal target range for a tank running co2, then how are people keeping shrimp/snails in a planted tank? Sure my plants' lower end is 6.5, and some shrimp and snails can go to 6.8, but maintaining at that level doesn't seem healthy to me. Am I missing something?

With no CO2 in my tank, and with plants I was at 6.7 pH. Obviously I can't push that 1.0 - 1.2 lower, or else I run risk of ruination of my plants.

My question is: should I raise the KH of the tank with a buffer, so that I can inject enough CO2 to get that 1.0 pH lower value? Is this what other people do? If not, how do people maintain a tank that is in the 6.5 - 7.0 range?

Edit: I don't have livestock in the tank, yet. I wanted to get my plants in and everything stable before adding them.

 

If 6.5-6.3 is an ideal target range for a tank running co2, then how are people keeping shrimp/snails in a planted tank? Sure my plants' lower end is 6.5, and some shrimp and snails can go to 6.8, but maintaining at that level doesn't seem healthy to me. Am I missing something?

Yes, you are missing something - Ideal target range starts at a 1.0 drop in pH from using CO2. From there you can go up slightly, over a few days / weeks, until you maximize CO2 levels without affecting livestock. 1.0 is a good starting point. pH is not a definitive parameter in terms of keeping shrimp / fish / plants / snails. The exact pH number means nothing in terms of keeping livestock or plants. Fish, shrimp and snails can live happy healthy lives in pH's into the 5's without issue. Remember, a pH drop from CO2 is not the same as a swing in pH from mineral contents. It does not harm the animals or plants.

With no CO2 in my tank, and with plants I was at 6.7 pH. Obviously I can't push that 1.0 - 1.2 lower, or else I run risk of ruination of my plants.

I doubt that number. How are you testing pH? What is the kH of the tank? What substrate are you using?

My question is: should I raise the KH of the tank with a buffer, so that I can inject enough CO2 to get that 1.0 pH lower value? Is this what other people do? If not, how do people maintain a tank that is in the 6.5 - 7.0 range?

No, never raise the kH. The lower the better. No successful planted tanker is aiming for a specific pH in the 6.5 - 70 range, they are aiming to drop the pH of their water by 1.0 - 1.4 from CO2 usage, regardless of their pH. Active substrate (ADA aquasoil style substrates) tanks are a little different, as they have 0 kH and a starting pH ~ 6.5.

Edit: I don't have livestock in the tank, yet. I wanted to get my plants in and everything stable before adding them.

See bold ^^

 

"I doubt that number. How are you testing pH? What is the kH of the tank? What substrate are you using? "

I've tested pH using the API master test kit, and using my calibrated pH controller. Prior to putting in the plants, I just had the API test kit, and it read 7.4-7.6. I added plants and put in the calibrated pH probe and it measured 6.7ish. I confirmed this with API test kit.

I don't yet know my kH. I have a test kit on order and should get here this week. I'm on municipal water, and it's softer. I lived most of my life on well-water that was hard water, and I can tell it's certainly not that.

Substrate is Seachem Flourite Black.

"...a pH drop from CO2 is not the same as a swing in pH from mineral contents. It does not harm the animals or plants."

This is the first time I've ever read this statement! So when I see that a plant or animal has a preferred pH range of 6.8 - 7.5, that's "base water pH", and not "pH after it's been injected with CO2" ? So, then you're saying if my tank with just plants and hardscape is at a given level, I can still use CO2 to lower that another 1.0, and while it registers as a drop in pH, it's not really a drop in pH?

Edit: I just turned off everything but the HOB. I'll give it the rest of the day and then tonight when I test parameters, I'll record everything.

 

I struggled with guppies and snails around that same ph. Try 1lb of crushed coral per 10 gallons and see if that helps with tds. You can find inexpensive tds meters on amazon when things get close to normal.

 

As of this morning, with nothing but the HOB filter running, the pH was 7.42. I've started CO2 into the tank, and will check in a few hours to see how low it's become. The CO2 drop checker is quite blue.

Also, my recent order has been slowed down; now it doesn't seem I'll get my KH test kit until Tuesday.

 

As of this morning, with nothing but the HOB filter running, the pH was 7.42. I've started CO2 into the tank, and will check in a few hours to see how low it's become. The CO2 drop checker is quite blue.

Also, my recent order has been slowed down; now it doesn't seem I'll get my KH test kit until Tuesday.

A degassed pH of 7.4 means your kH is likely ~3 - 6 degrees. That is plenty, do not add anything to adjust kH like crushed coral, it will "harm" plants.

Drop the pH of the tank to 6.4 to start, that is a very safe drop.

You are correct, those "preferred" pH values are just a baseline, the vast majority of common aquarium fish can live in massively different pH's without issue.

Dissolved CO2 created carboxylic acid, which is a very weak acid, thus lowers the pH. But, it does not change mineral content / osmotic pressure so it goes un-noticed by the livestock. Too much and you'll see them gasping at the surface... but that's not pH related, that's just too much CO2 being driven into the tank. When running pH drops 1.2 or larger I recommend an airstone on a timer to run at night only to maximize gas exchange, and always ensure your filters are creating a small but noticeable ripple effect across most of the tank surface. You've got a hang on back filter, so you should have very good gas exchange rates as is.

For reference, my 25 gallon tank with moderate - moderately high surface agitation was running 4.75 bubbles per second into a reactor (100% diffusion) dropping my pH from 7.1 - 5.8 with zero livestock issues.

 

Thanks, Chanyi.

As of now, the tank is at 6.69, and I'm putting in CO2 with about 2.5 bps. I'll see where it's at after I get my 2-hour call here.

I got the remainder of my plants yesterday, and they've in their recovery bath from the alum soak last night. I'll be adding these to the tank later this afternoon.

 

So yesterday, using co2, the tank went to 6.1. At 5am this morning it was back up to 7.5, having run an airstone all night. I've turned the airstone off, but won't start co2 until an hour prior to the lights coming on.

I did get my drop checker to be lime green yesterday, at some point, so I'm feeling positive about that. I'm wondering if trying to dial this in without livestock is making it tougher?

I don't plan for a heavily stocked tank anyways (one betta, snails, and shrimp) for 20g. I still just cringe at the idea of the tank being too acidic during the day and then too anaerobic at night.

 

I still just cringe at the idea of the tank being too acidic during the day and then too anaerobic at night.

Can you elaborate on this a bit?

6.1 is no where near too acidic.

1.0 drop from your tank's degassed pH value, try and achieve this drop by the time the lights come on, or shortly after.

anaerobic means no oxygen... there will be plenty of O2 at night for plants / livestock and bacteria.

 

Yes, anaerobic wasn't the right word there....I just worry that my drop checker is dark blue by the time morning hits and has been around 7.4 pH then. Turn up the CO2 before lights and get it down. It's 6.2 now, and now what? Do I keep adding CO2? Crank it down to 1 bubble per second and see if it holds?

My fear is that this up and down and up and down on CO2 is going to cause an algae outbreak even before the plants have a chance to settle in and root. If "stable CO2" or "no wide CO2 swings" is one thing that helps keep algae at bay, am I already screwing up? Or is a 7.5 to 6.2 swing not considered a "wide swing"?

I can only guess that when I have livestock in the tank and have fauna adding CO2 from respiration, that it may stabilize more during the day than I feel it does now. I seems as if I'm on a see-saw: bring it down, cut it back/off, up it goes, turn it on, bring it down...........

 

You are overthinking this.

Plants will only use CO2 when there is light present.
When light is not present, plants reverse and respire O2.

CO2 consistency is only needed through the photoperiod. Dropping the pH by 1.0, and keeping it at the 1.0 drop throughout the photoperiod is all that's needed. It can then go back up to 7.5 at night with 0 issue.

Drop checkers have a 2-3 hour delay, so just because it's blue when then lights come on, doesn't mean you aren't at the 1.0 drop. It's blue because 2 hours before the lights came on, the CO2 was not on.

Up and down CO2 "swing" is perfectly fine when the lights are off, it's the day-day inconsistencies when the lights are on that causes issues. Plant cells develop to use a certain ppm of CO2, if that level is constantly changing throughout the photoperiod, the plant cells will be constantly chasing the correct enzyme / protein build ups.

Typically, the CO2 will cause pH to drop rather quickly when the lights are off (because no plant uptake) and then it will plateau. With trial and error, you can get it to plateau at the 1.0 mark just as the lights come on (or shortly after) and now you're maintaining consistent CO2 throughout the entire photoperiod. This comes naturally with plant uptake of CO2.

For reference:

My 25 gallon tank ran with 4.75 bubbles per second into a reactor with 100% dissolution droping my pH from 7.1 to 5.8 within 3 hours. I turned my CO2 on 2 or 2.5 hours before the lights came on (I can't remember as that tank is torn down now), and ran CO2 all the way until the lights shut off. I then had an airstone running for 8 hours through the night. Lights were on for 7.5 hours per day, CO2 for 9.5 hours or so. My kH was 1.0 degrees, and my surface agitation was on the higher end (off-gassing a decent amount of CO2, thus why my bubbles per second was high).

My fish, shrimp, snails and plants were all healthy as can be.

 

Also, ChanyI thanks for taking the time to explain all this to me.

 

If you're 4.75 bps had it drop over the course of 3 hours, did you manually adjust it to a slower speed at that, to keep a steady rate?

Now I get why KH is so important, it's lets you know approximately what pH has 30ppm. Until I get that test kit on Tuesday, I don't know what my KH is, and what my 30ppm target should be (though, like you say it's probably around 6.2).

 

If you're 4.75 bps had it drop over the course of 3 hours, did you manually adjust it to a slower speed at that, to keep a steady rate?

Now I get why KH is so important, it's lets you know approximately what pH has 30ppm. Until I get that test kit on Tuesday, I don't know what my KH is, and what my 30ppm target should be (though, like you say it's probably around 6.2).

No kH does not give you anything in regard to CO2, it determines your starting pH and how much CO2 is needed to drive pH down.

The kH / CO2 / pH chart you see floating around is not accurate, Tom Barr himself admitted it. It assumes the only thing affecting pH is carbonates and CO2, which is not the case in our tanks. It's a ballpark estimate at best.

Drop checker / pH drop is a much better indication (drop checker is a pH reaction with CO2 technically, so pH drop is our only way of measuring CO2 at the hobby level).

And no, 4.75 bubbles per second from 12:30 in the afternoon until 10:30pm the CO2 is at that rate, and the pH dropped to 5.8 and stayed there until the lights went out, CO2 shut off, and airstone turned on, where the pH then rose to 7.1 as the CO2 off-gassed.

 

ChanyI ... I was able to test my aquarium water kH today...it's at 6*dKH. That's actually a little higher than I thought it would be. But my tap water is about 3*dKH. Does this make any sense?

 

ChanyI ... I was able to test my aquarium water kH today...it's at 6*dKH. That's actually a little higher than I thought it would be. But my tap water is about 3*dKH. Does this make any sense?

What rocks are in the tank?
Any other hardscape?
What substrate do you have again?
How do you top-off evaporation? Using tap water to top-off evaporation coupled with less than 50% water changes would result in kH / gH / TDS increasing.

 

What rocks are in the tank?
Any other hardscape?
What substrate do you have again?
How do you top-off evaporation? Using tap water to top-off evaporation coupled with less than 50% water changes would result in kH / gH / TDS increasing.

Hardscape:

• 5 pieces Ecoscape Temple Stone (claims to be inert and not change water pH or hardness)
• 3 pieces of driftwood
• 3 ceramic "caves"

Substrate:

• Seachem Flourite Black

I haven't topped off any evaporation; the tank has a closed glass lid, and the water level hasn't really changed; I'm guessing the condensed vapor is dripping back into the tank. But, I haven't done any water changes as of yet.

 

I know they claim that, but I'm going to blame that stone for leaching some cabonates (kH) into the water...

Seyriu stone does the same thing.

 

I know they claim that, but I'm going to blame that stone for leaching some cabonates (kH) into the water...

Seyriu stone does the same thing.

Should I worry about? What should I do to balance it? Should I do anything at all?

 

If 6.5-6.3 is an ideal target range for a tank running co2, then how are people keeping shrimp/snails in a planted tank? Sure my plants' lower end is 6.5, and some shrimp and snails can go to 6.8, but maintaining at that level doesn't seem healthy to me. Am I missing something?

With no CO2 in my tank, and with plants I was at 6.7 pH. Obviously I can't push that 1.0 - 1.2 lower, or else I run risk of ruination of my plants.

My question is: should I raise the KH of the tank with a buffer, so that I can inject enough CO2 to get that 1.0 pH lower value? Is this what other people do? If not, how do people maintain a tank that is in the 6.5 - 7.0 range?

Edit: I don't have livestock in the tank, yet. I wanted to get my plants in and everything stable before adding them.

TBH shrimp like neos don't really thrive in a high tech tank due to the PH changes and lower PH. If you are looking to add shrimp I'd use amanos.

 

neos are fine high tech, never have I had issues.

Should I worry about? What should I do to balance it? Should I do anything at all?

No don't worry, just keep an eye on it over time, nothing you can do unless you want to start scrubbing kH with HCL, which is fairly tough even for the most experienced planted tankers.

 

No don't worry, just keep an eye on it over time, nothing you can do unless you want to start scrubbing kH with HCL, which is fairly tough even for the most experienced planted tankers.

Once cycled, with weekly water changes, it should help, right?

 

neos are fine high tech, never have I had issues.

No don't worry, just keep an eye on it over time, nothing you can do unless you want to start scrubbing kH with HCL, which is fairly tough even for the most experienced planted tankers.

I've gotten them to breed but very seldom. Same with using buffering substrates. Maybe I'm doing something wrong but I find they want a pretty high KH and no CO2.

 

Once cycled, with weekly water changes, it should help, right?

Yes it should help.

 

Once cycled, with weekly water changes, it should help, right?

Yep, if your KH starts to go up overtime you will see it in a PH increase. If you are keeping inverts you want a little KH in there anyways and 4dKH is my typical target.

 

If you are keeping inverts you want a little KH in there anyways and 4dKH is my typical target.

Any specific reason as to why this is your typical target?

 

Any specific reason as to why this is your typical target?

I prep water for my tanks in bulk, and I don't have an RO system yet. Most plants and critters will be happy with 4dKH, if you go over 8 some plants will get stunted, if you go below 2 you don't have much buffering capacity and if that gets eaten up the PH can swing severely. Now the tanks with buffering substrate would prefer no KH as it eats up their capacity, but I feel as though 4 is low enough to not shorten their life too severely. Again that it out of lazyness because I don't want to have to prepare different batches of water for different tanks.

Locally our municipal water is treated with a strong base, I believe it's sodium hydroxide. Out of the tap I have a PH of 8.2-8.4 and a KH of 1 and GH of 2. Since the KH is so low just a tiny amount of acid buffer will shoot the PH down. So I dose with acid buffer and drop the PH down to 6.5 then add GH and KH buffers to bring my KH to 4 which bumps up the PH to 7ish. Then I bring the GH up to about 4-5 or whatever gives me a TDS around 200.

 

I prep water for my tanks in bulk, and I don't have an RO system yet. Most plants and critters will be happy with 4dKH, if you go over 8 some plants will get stunted, if you go below 2 you don't have much buffering capacity and if that gets eaten up the PH can swing severely. Now the tanks with buffering substrate would prefer no KH as it eats up their capacity, but I feel as though 4 is low enough to not shorten their life too severely. Again that it out of lazyness because I don't want to have to prepare different batches of water for different tanks.

Locally our municipal water is treated with a strong base, I believe it's sodium hydroxide. Out of the tap I have a PH of 8.2-8.4 and a KH of 1 and GH of 2. Since the KH is so low just a tiny amount of acid buffer will shoot the PH down. So I dose with acid buffer and drop the PH down to 6.5 then add GH and KH buffers to bring my KH to 4 which bumps up the PH to 7ish. Then I bring the GH up to about 4-5 or whatever gives me a TDS around 200.

So it sounds like your particular water source is an outlier, and you require several times the steps as the majority of tap water users. This might be why you've had issues with neos in the past.

A kH of 0.5 - 1.0 is enough to keep the pH stable. It was been vastly tested by experienced users. a kH of 1-2 will not cause massive pH swings with the smallest amount of acid buffer, also, what exactly would cause a random spike of an acid buffer in a tank? But again, your water source is more challenging and may give you these issues more so than others.

99% of plants prefer the softest water possible.

Most common aquarium fish (African cichlids and livebeares excluded) prefer very soft, slightly acidic water.

 

So it sounds like your particular water source is an outlier, and you require several times the steps as the majority of tap water users. This might be why you've had issues with neos in the past.

A kH of 0.5 - 1.0 is enough to keep the pH stable. It was been vastly tested by experienced users. a kH of 1-2 will not cause massive pH swings with the smallest amount of acid buffer, also, what exactly would cause a random spike of an acid buffer in a tank? But again, your water source is more challenging and may give you these issues more so than others.

99% of plants prefer the softest water possible.

Most common aquarium fish (African cichlids and livebeares excluded) prefer very soft, slightly acidic water.

You could be right about my shrimp breeding woes, even now I have a planted tank with buffering substrate and CO2 running around 20PPM and I have a few Neos in there but they won't breed and I've noticed some carapace discoloration which I'm assuming is a molting problem. In the same tank the Amanos are molting no problem so I can only assume they are happier about their environment. I'm going to rehome the neos in a new shrimp tank I'm setting up. With my same water, inert substrate and no CO2 the Neos breed. So I just kinda thought they didn't like the low KH and PH swings from the CO2...but this was just me making assumptions.

As for PH buffer this wasn't exact science science, it was just a hunch and one I gathered on my own. I was of the understanding that as organic materials break down they produce acid and eat away at the KH, and once the KH is consumed the PH goes nuts. So I targeted 4 because it was a number which it seemed most fish and plants were happy with, and it would give me a solid buffer.

I took my source water, tested the KH and then started adding acid buffer until the KH was 0 and the PH dropped like a rock. I had only about 1/8 of a teaspoon until that happened. I guess that made me a little gun shy.

 

The acids produced my decomposition is are very weak, and even with regular small water changes, you remove enough, and replace with more carbonates to keep the pH stable even at very low kH / carbonate levels.

In - tank pH crashes are like fishing tales, very rarely do you see any amount of evidence to support the claims.

Your acid buffer would be many times stronger than decomposition acids, and thus would drop your pH dramatically without any carbonates to buffer it.