Low pH--co2 injection plus fresh aquasoil....is this right?

Fishstery

I just started my first co2 injected setup and am in the process of trying to dial in my co2. Currently I have the solenoid turning on one hour before lights on and one hour before lights off. I have it set to about 1 BPS so 60 BPM. The drop checker is blueish green when the lights come on and after about 3-4 hours the drop checker hits light green. I have fish in the tank that require higher levels of DO so I run an airstone during lights off to help gass off any excess co2. This is the first time I'm checking pH since my fish haven't seem stressed from the co2 and the drop checker isn't yellow, but my pH is at the very least 6.0 but may be even lower since the vial turned yellow immediately after adding the pH solution. I should note that I also have fresh UNS contrasoil in here which IME will lower pH around 6.2 until it "ages" and it will eventually buffer the pH to 6.4-6.6. Does a very low pH sound right to you guys even if the drop checker is showing green?

Tank is a 12gal long and my tap pH is a 6.6 and then 6.8 after it gasses out. I just set up the co2 and aquasoil 48 hrs ago.
 

Frank the Fish guy

Sounds about right.

Your soil is buffering the pH of the water to be low (acid buffer). Then you are adding C02 which will lower it further. So you could be having a pH of 6.0. If your pH tester can't register lower than 6 you should get a test that can.

The drop checker is isolated from the tank water and is only measuring the C02 portion of the water, so it is not supposed to be affected by your acid buffer soil. That is why it has the air gap between the solution and your tank. You are going to have to trust your drop checker as the monitor for the C02 level and just ignore the pH since it has been altered and buffered by your soil.

Once you use a soil that buffers the pH, you can't really use pH as an indirect indicator of other stuff like C02 concentration.
 
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Fishstery

Sounds about right.

Your soil is buffering the pH of the water to be low (acid buffer). Then you are adding C02 which will lower it further. So you could be having a pH of 6.0. If your pH tester can't register lower than 6 you should get a test that can.

The drop checker is isolated from the tank water and is only measuring the C02 portion of the water, so it is not supposed to be affected by your acid buffer soil. That is why it has the air gap between the solution and your tank. You are going to have to trust your drop checker as the monitor for the C02 level and just ignore the pH since it has been altered and buffered by your soil.

Once you use a soil that buffers the pH, you can't really use pH as an indirect indicator of other stuff like C02 concentration.
Thank you for clarifying that for me! The aquasoil in a tank without co2 dropped the pH to around 6-6.2 for at least a month or two, now the pH is at 6.4 so atleast I already had an idea of how it affects my tap water. I don't have a kH test and was wondering if that was a necessity now that I'm injecting co2 or am I able to just simply rely on the drop checker? The drop checker came with a solution (niclog brand) that claims the solution is 4 dKH
 
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Mudminnow

Your tank sounds good to me. Many high tech planted tanks run soft and acidic. Your pH could be going down to 5.0 (lower if everything still seems healthy), and I still wouldn't worry.
 
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Fishstery

Your tank sounds good to me. Many high tech planted tanks run soft and acidic. Your pH could be going down to 5.0 (lower if everything still seems healthy), and I still wouldn't worry.
Thank you! I actually read this article previously when I first added my aquasoil in my pond tank and was concerned about the low pH "crashing my cycle". It's a great read. I would also say there is very little truth behind correlation in pH and bacterial colonies, as that tank has maintained a pH value below 6.6 since March and hasn't had any ammonia or nitrite spikes and I also used preseeded media that came from tanks with less acidic water. Im wondering if my lighting and co2 is too much for the plants I'm growing, I'm running about 25-32 watts on a 12 gal (actual volume is 9 gals) so approximately 3-4 watts per gallon and then 1 bubble per second on my co2. Does anyone know if there needs to be a "warm up" period like running slightly less co2 until my plants start to root in? They are all freshly planted tissue culture plants, so I'm expecting some portions to melt off while the new growth starts. Do I need to dial back the co2 until the plants grow in fuller and need more nutrients, or can I just "blast" the co2 from the beginning? I also haven't dosed any ferts yet and wasn't sure if I should or shouldn't. I'm growing dwarf hairgrass, Monte Carlo, utricularia graminifolia, hydrocotyle Japan, and Christmas moss.
 
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Mudminnow

I've always run my CO2 to get about 30ppm right from the start. I've read that plants take a while to adjust to CO2 levels. Therefore, I keep the levels the same right from the start. I figure, that makes it easier on them.

Regarding fertilizers. I'm less certain. With trees, for example, it is best not to offer too much (if any) fertilizers right after planting. The reason being that trees will use their available energy for growing instead of self defense, if fertilizers are used--not so great given the stress of transplanting. Still, I'm not too sure how similar our aquarium plants are to trees. And, I wouldn't know just how much to step up the ferts and when. Therefore, I've always just dosed my tanks 100% right from the start. It seems to have worked so far.
 
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Fishstery

I've always run my CO2 to get about 30ppm right from the start. I've read that plants take a while to adjust to CO2 levels. Therefore, I keep the levels the same right from the start. I figure, that makes it easier on them.

Regarding fertilizers. I'm less certain. With trees, for example, it is best not to offer too much (if any) fertilizers right after planting. The reason being that trees will use their available energy for growing instead of self defense, if fertilizers are used--not so great given the stress of transplanting. Still, I'm not too sure how similar our aquarium plants are to trees. And, I wouldn't know just how much to step up the ferts and when. Therefore, I've always just dosed my tanks 100% right from the start. It seems to have worked so far.
I'm weary about ferts because of the UG which is by far the most difficult plant I have in there. I avoided planting it in aquasoil (I've had OK success growing it partially emersed in aquasoil) but apparently water parameters need to be pretty consistent for UG not to randomly melt. I already know I deal with excess phosphates in my tap water due to cyanobacteria that I deal with in most of my tanks from time to time, but after dosing DIY co2 on my 29 gal I found that the cyano started to die off once my plants took off. I'm wondering with my plant selection if I even need an all-in-one fert or if I should just find a liquid fert for nitrite since my nitrite levels are always below 5ppm
 
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Mudminnow

I've never tried growing UG, so I can't really offer any help with that. I've always been a bit afraid of trying it given it's reputation for being hard to grow. I'd be curious to know how your experience goes though.
 
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Frank the Fish guy

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3– ↔ 2 H+ + CO32–

What this means is that when you add C02 to your tank, C02 and water create a balance of hydrogen ions and bi-carbonate, and also a balance of hydrogen ions and carbonate.

The pH measures the newly created hydrogen ions, which means the pH is lowered as you add C02.

But the bi-carbonate has been created too. The bi-carbonate is used by your bacteria and the nitrogen cycle continues regardless of how low the pH goes.

You don't need to wait to grow a new colony of new bacteria that thrives in low pH water (that takes too long), instead the C02 itself is creating the bi-carbonate needed to keep the cycle going.

This extra bi-carbonate does not show up on our KH test kits since the test kits are measuring calcium carbonate and inferring the carbonate level. The test is not directly measuring carbonates, so when these carbonates are created from C02, they don't show up on the KH test, but they are in the water and feed the cycle. If you read the fine print, the test says it reports calcium carbonate only.


Carbonate crashes directly cause the nitrogen cycle to stop. This is well documented. You will find lots of threads on Fishlore where folks have low pH and 0 KH and their cycle stops. Adding a bit of carbonate fixes the crash straight away. Most folks use crushed coral, soda ash, or baking soda, or other forms of calcium carbonate. These will add carbonate AND will show up on your KH test. But you can add C02 too! This is what happens in nature in soft water systems. The C02 supplies the carbonates.

But this will make aquarium people's heads spin. If someone has a pH crash with pH at 6.0, the solution is to lower the pH further by adding C02! Ughh!!!! But it's true.

So the crashes occur due to having zero carbonates. The low carbonates also cause the pH to crash which is what is measured.

At a pH of 6.0 the nitrogen cycle stops since the carbonates have been depleted.

But for you OP, you are dropping the pH while also adding carbonates. No crash. No problem. And no, you don't need to grow new exotic bacteria. Your same bacteria colony will continue as is.


I think that the fact that we have this little test bottle called KH that says it measures carbonate hardness, yet it does not measure carbonates, is tremendously confusing! But there is no carbonate test. And the carbonates are what the bacteria need, they don't actually care about the pH.
 
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Fishstery

Just an update for you guys, I haven't gotten time yet to retest the pH, I also got a kH/gH test kit which I will do this weekend. However, I got the co2 dialed in nicely, about 1 bubble per second and by the time I get home from work and the co2 has just shut off my drop checker is light green, and then once the lights go out I plug in the airstone. My rainbow shiners have been doing well with the co2. As far as plants, there's already tons of new growth after just one week, most of the old growth is melting off which is expected, but I also planted the monte carlo in large clumps so I assumed everything underneath would melt anyways. The UG is actually growing the fastest, with new "leaves" sprouting up everywhere. I have had more monte carlo and hairgrass float up than UG, so I'd say planting it in inert sand is a success. The sand helps keep it "rooted" down. Currently I am dosing thrive c for low tech setups once a week (bottle suggests twice) and once the plants start growing more I will switch to thrive + for high tech systems(much more nitrate and nutrients than thrive c) and slowly up the dosage amount. Since the plants are still small and growing I don't want to overdose the ferts and cause algae issues. I also don't want to have excess ferts in the water column and melt my UG. I'll update again after the weekend.
 
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Frank the Fish guy

C02 is poison to fish once it gets too high. Meanwhile plants will do well at lower levels. Always good to keep the C02 just low enough to make your plants (and you) and your fish happy!

You may want to rethink 'ferts' once you get used to C02. C02 is the main fertilizer that plants need, along with an iron source from the soil.
 
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Mudminnow

CO2 + H2O ↔ H2CO3 ↔ H+ + HCO3– ↔ 2 H+ + CO32–

What this means is that when you add C02 to your tank, C02 and water create a balance of hydrogen ions and bi-carbonate, and also a balance of hydrogen ions and carbonate.

The pH measures the newly created hydrogen ions, which means the pH is lowered as you add C02.

But the bi-carbonate has been created too. The bi-carbonate is used by your bacteria and the nitrogen cycle continues regardless of how low the pH goes.

You don't need to wait to grow a new colony of new bacteria that thrives in low pH water (that takes too long), instead the C02 itself is creating the bi-carbonate needed to keep the cycle going.

This extra bi-carbonate does not show up on our KH test kits since the test kits are measuring calcium carbonate and inferring the carbonate level. The test is not directly measuring carbonates, so when these carbonates are created from C02, they don't show up on the KH test, but they are in the water and feed the cycle. If you read the fine print, the test says it reports calcium carbonate only.


Carbonate crashes directly cause the nitrogen cycle to stop. This is well documented. You will find lots of threads on Fishlore where folks have low pH and 0 KH and their cycle stops. Adding a bit of carbonate fixes the crash straight away. Most folks use crushed coral, soda ash, or baking soda, or other forms of calcium carbonate. These will add carbonate AND will show up on your KH test. But you can add C02 too! This is what happens in nature in soft water systems. The C02 supplies the carbonates.

But this will make aquarium people's heads spin. If someone has a pH crash with pH at 6.0, the solution is to lower the pH further by adding C02! Ughh!!!! But it's true.

So the crashes occur due to having zero carbonates. The low carbonates also cause the pH to crash which is what is measured.

At a pH of 6.0 the nitrogen cycle stops since the carbonates have been depleted.

But for you OP, you are dropping the pH while also adding carbonates. No crash. No problem. And no, you don't need to grow new exotic bacteria. Your same bacteria colony will continue as is.


I think that the fact that we have this little test bottle called KH that says it measures carbonate hardness, yet it does not measure carbonates, is tremendously confusing! But there is no carbonate test. And the carbonates are what the bacteria need, they don't actually care about the pH.
This is interesting to me. And, to be honest, I don't entirely understand it. I had thought (quite possibly incorrectly) at least some nitrifying bacteria operated independently of calcium carbonates. I remember reading this article: Nitrification in a Biofilm at Low pH Values: Role of In Situ Microenvironments and Acid Tolerance (nih.gov). One section of this study stood out to me in regard to carbonates: "The system was supplied with bicarbonate in stoichiometric amounts to the nitrification rate. No difference in pH or oxygen microprofiles or in local conversion rates was found between biofilms grown on both materials. This similarity strongly supports our hypothesis that pH, within wide limits, does not primarily control growth and activity of nitrifiers. Our findings are in line with the observation that the increased addition of calcium carbonate to acidic tea soils does not affect nitrification rate."

Is there more than anecdotal evidence that nitrifying bacteria need carbonates? Could there be something else causing the crashes that people observe? I'm pretty clueless here. But, your post made me curious.
 
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Frank the Fish guy

This is interesting to me. And, to be honest, I don't entirely understand it. I had thought (quite possibly incorrectly) at least some nitrifying bacteria operated independently of calcium carbonates. I remember reading this article: Nitrification in a Biofilm at Low pH Values: Role of In Situ Microenvironments and Acid Tolerance (nih.gov). One section of this study stood out to me in regard to carbonates: "The system was supplied with bicarbonate in stoichiometric amounts to the nitrification rate. No difference in pH or oxygen microprofiles or in local conversion rates was found between biofilms grown on both materials. This similarity strongly supports our hypothesis that pH, within wide limits, does not primarily control growth and activity of nitrifiers. Our findings are in line with the observation that the increased addition of calcium carbonate to acidic tea soils does not affect nitrification rate."

Is there more than anecdotal evidence that nitrifying bacteria need carbonates? Could there be something else causing the crashes that people observe? I'm pretty clueless here. But, your post made me curious.
What this means is that as long as there is some carbonate then adding more will NOT increase the rate of nitrification. So you can keep the carbonates (and pH) in a very wide range and it will have no effect on the amount of nitrification. That is what they confirmed.

The bacteria use the carbonate in the nitrification process. Tanks that have no source of carbonate have a KH value that depletes over time. So what matters is the rate that it is used and replenished. As long as the carbonates don't go to zero then nitrification continues. When carbonates drop to zero, nitrification stops abruptly. This is the pH=6.0 value for water (with nothing else in it to alter the pH). I have rescued many tanks where the KH went to 0 and the biofilter stopped completely. Here is a thread for example: Fishless cycle dilemma/stalled | Aquarium Nitrogen Cycle Forum | 463164


But if you add additional carbonates beyond the minimum needed, you don't get more nitrification. This is why you can set KH to be anything you want, and a KH value of 5 is good to keep the tank stable. The extra carbonate is a buffer so if there is a sudden need for your bio-filter to increase - a dead fish for example, then the carbonates are there in reserve to support the bio-filter.

Then you can pump in C02 and the carbonates will increase further, but the pH will drop. As you pump more C02, your carbonates go up, but this has no measurable effect on the bio filter.


Since the topic is low pH water, the thing to be concerned with when you have a low pH tank is the fact that nitrite is much more toxic at low pH. Meanwhile, ammonia is the opposite. For a tank with pH=6.0, the ammonia is not toxic at all in practice, but nitrite is toxic at low measurable levels. (.25 - .5 ppm).

So you should keep an eye on nitrites to monitor your biofilter if you are running at low pH.

Nitrites should always be zero, if they become measurable in a low pH tank you need to dilute them immediately in a low pH tank.

This is actually why we measure pH. It tells us how to interpret the nitrite and ammonia levels to know if they are toxic.
 
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Fishstery

Just an update for you guys, here's a 1 week update since aquascaping and setting up the co2. As you can see I have a great amount of growth so far, especially the UG which you can see first in the foreground in the sandy areas. The top photo was today after the first WC and trim and the bottom photo was directly after setup. I think avoiding planting the UG in the aquasoil areas and using sand to plant it was key to success. After getting a tiny bit cyano starting I have stopped dosing water column ferts after the first time, I will give the plants another week to develop before trying ferts again. Fish seem to be fine at 1BPS and the drop checker being lime green, once lights go out I plug in the airstone for them overnight and this seems to work well for my shiners.

IMG_20210613_173349.jpg
 
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