Betta splendens in acidic water with CO2

Hello! I'm currently setting up a tank for a betta. It's a decently planted 60L (about 16G) tank that currently only houses some ramshorn snails but I eventually want to house a giant betta in. It's currently in the tail end of cycling with no ammonia and nitrites and about 10-20 ppm of nitrates. My question is about pH that a domesticated betta splendens can be OK with. The online shop I eventually want to buy from recommends a pH of between 6-7.



My tank above is currently reading at around 5.8 (my API test kit can't read that low, so this is what the Seachem pH Alert is roughly telling me). The low pH is caused by a few factors:
- 0 dKH and about 6 dGH. I'm using RO water remineralised with Seachem Equilibrium.
- Aquasoil. I'm using fresh ADA Amazonia, I'm guessing about 8 litres of it.
- A hardscape of wood and lava rocks. I've just removed some wood and replaced it with some lava rock today in the hopes it'll eke my pH slightly higher.
- CO2 injection. Injection happens 24/7 via a DIY system. The drop checker is lime green so I'm guessing that's contributing to a pH drop of around 1?

I've purposefully not added any KH or any rocks that will leech calcium into the water as I want try and keep the buffering capacity of the aquasoil for as long as possible, which is also why I stick to RO water instead of treated tap water.

My rough understanding is that low pH from CO2 injection doesn't factor into fauna parameters and that as long as the pH is kept stable and kinda sorta neutral sans the carbonic acid, it's OK? I was hoping to add a little bit of tannins in the future as well via leaf litter or IALs, is that a pipe dream with how close to the edge my pH is?

 

First of all: Soft and acidic is optimal for softwater fish like Bettas. I'd advise to NOT get a domestic (=/= domesticated), though. They are overbred, ridden with health problems (even if no pathogens or parasites are involved) and have short livespans. If any chose a fish that is as close as possible to wild forms or directly get a wild species like Betta imbellis or Betta smaragdina.

Not so optimal: 0°KH and CO2. This is a recipe for disaster unless you regulate CO2 via a pH sensor that stops injection once a certain pH is reached.
With 0 KH you can easily cause a pH-crash with CO2 injection. There are only 3 ways of causing one:
a. low KH, no waterchanges, high stocking density, Nitrates (solved as nitric acid) under the roof. (doesn't apply here)
b. low KH, uncontrolled CO2 injection.
c. low KH (unknown to the owner), and trial and error-technique using pH-down products directly on the tank instead of pretreatment.

And your setup is snap-bang in the b.-section.

- Aquasoil. I'm using fresh ADA Amazonia, I'm guessing about 8 litres of it.

Keep in mind the stuff will only work for a certain timeframe. Over time it will lose its properties. No matter what water you use, because while yes, the KH of the sourcewater factors in, the dilution is more important, so after a number of waterchanges it will get depleted.

My rough understanding is that low pH from CO2 injection doesn't factor into fauna parameters and that as long as the pH is kept stable and kinda sorta neutral sans the carbonic acid, it's OK?

Easy to cross the line of healthy amounts. Also if you don't turn off injection overnight any fish that isn't able to breathe air (yes, Bettas can but will still be stressed) will probably suffocate, as at night plants release CO2.
If you look at the charts showing the connection of KH, pH and CO2 you will see, that at 0°KH and a pH of 6, the CO2 dissolved is already in a range considered good for plants but also high for fish.

I was hoping to add a little bit of tannins in the future as well via leaf litter or IALs, is that a pipe dream with how close to the edge my pH is?

You have two options to buffer pH reliably and safely:
- KH. Simple equation: The higher the KH, the higher the pH. Buffers in higher (pH 7 or more) ranges. Buffer of choice when using CO2.
- humic substances (aka "tannins"). Buffers in the low ranges between 4 and 6. If used correctly as the only buffer usually ends up around a pH of 5. Does not buffer pH against CO2, but allows for a good solubility of CO2 from the air and makes injection redundant.
Hint: Strong colour in the water makes for poor plant growth under a ceertain depth.

My recommendation:
Either:
- Raise KH to at least 3-4° as a safe-fail against over-injection. (May become expensive and error-sensitive in case you forget remineralizing the water for a waterchange.)
OR
- Regulate CO2 injection via a pH-sensor, stopping injection at a certain pH. (Quite an investment in tech necessary. DIY won't be possible anymore unless you are a technician.)
OR
- Toss the idea of CO2-injection, do a softwater tank with humic substances, focused on the fish and their habitat and not on underwater gardening. (Longterm the cheapest, least maintenance-heavy and imo most satisfying option.)

 

Suppose you like to garden underwater (hi MacZ), I'd be more concerned with a steady CO2 supply than anything else as plants are highly attuned to this.

And the continuous release of CO2 at night.... what MacZ says. At least have the water surface strongly agitated at night. Although many, including yours truly, prefer permanent aeration.

Regarding soils....it's so complex that I've given up years ago. Not the theory but the practice. pH not right for plants? Not to worry, they'll adjust the pH for you by actively releasing H+ in exchange for certain minerals.

I turned to inert sand and get the same results eventually. The "inertness" is a characteristic of the silica sand, but the sand gets mixed with organic compounds and is constantly fed by minerals.

It's a bit the same with CO2 actually.

You really can get close to high tech tanks with low tech, but it takes more time. Plants release O2 via the roots to feed microbes, which in return deliver minerals and CO2... which plants are able to take in via the roots also. If CO2 is still low to their liking, they start to take in KH (not sure if this only pertains to "bipolar leaves" though).

"and that as long as the pH is kept stable and kinda sorta neutral sans the carbonic acid, it's OK?"

Only a tiny amount of CO2 is converted into carbonic acid, which converts further depending on pH....which swings due to CO2 differences, which....

Talking about headaches. I'd totally ignore pH in planted tanks. Plants are actively involved.

So for plants, do whatever you like, but keep CO2 supply steady.

For fish, I don't know how fish react to pH changes. I assume most if not all are attuned to fixed often dramatic patterns caused by CO2/plants or, because plants are often absent in natural bodies of water, but not the decomposing parts from hanging over vegetation that have fallen into the water, CO2/microbial activity.

Again, I'd worry more about CO2 and O2.

 

Thanks for the reply! I'm willing to go pressurised CO2 if necessary, I'm still fiddling with my recipes for this 60L tank. I took a look at pH controllers and it seems they don't really work without any KH?

With the humic buffering, I thought that was how aquasoil basically worked? ADA has said Amazonia contains a bunch of humic acid in it. I wasn't planning on making the tannins dark enough to completely buffer the pH by themselves so I would need to replace the aquasoil or convert to KH when it does eventually exhaust itself. Reading online, several sources seemed to indicate this is about 1-5 years. But humic buffering down to pH 5 is great, I don't feel so bad about my 5.8 as much.



I'm assuming the chart you're referring to is one like this? My pH is 5.8 after CO2 injection, I think in order to compare myself in that chart, I need to take a reading with my water without CO2. I might try to set some water aside and try to get a reading after the CO2 has gassed off. According to that though, if I have no KH, I can get away with half the CO2 injection I thought I needed...

Suppose you like to garden underwater (hi MacZ), I'd be more concerned with a steady CO2 supply than anything else as plants are highly attuned to this.

And the continuous release of CO2 at night.... what MacZ says. At least have the water surface strongly agitated at night. Although many, including yours truly, prefer permanent aeration.
...
Again, I'd worry more about CO2 and O2.

Yup, the soil and CO2 injection is what's making this all complicated! Your point about plants fixing pH themselves is fascinating, I'll have to read up on that. Glad to hear I don't have to worry about the pH as much though, thanks!
For your permanent aeration, do you mean a bubbler or just strong surface agitation by your filter outflow?

 

Active soils should be looked at as a bunch of minerals that gets slowly depleted over time and as a Cation Exchange Capacity, which stays pretty much stable over time. For instance, initially, typically H+ is exchanged for Ca+ and Mg+. Hence active soils, initially, lowers pH, KH, GH as it contains a lot of H+.

"about 1-5 years"? Depends on your source water. If very soft, yes, a few years.

Be careful with this chart. Better yet, don't use it! It's probably the most mis-used chart in the planted tank hobby. Your final remark is a prime example of this.

If you target 25 ppm CO2, you'll need to inject the same amount regardless if your water is KH low or high.

 

I'm approaching the topic from the opposite side of ruud, obviously. I'm specialized on fishkeeping and extreme softwater parameters.

I took a look at pH controllers and it seems they don't really work without any KH?

Many. There are some high-end probes that are independent of KH or conductivity.

With the humic buffering, I thought that was how aquasoil basically worked?

Partially. But not entirely. As I don't use the stuff myself the only thing I know is: The effect wears off with dilution by waterchanges. And going by observations of people that use it, the effects are gone after between 2 and 8 months depending on the specific product and the percentage and frequency of waterchanges.

I wasn't planning on making the tannins dark enough to completely buffer the pH by themselves

The colour of the water has no correlation to the amounts of humic substances. It is no reliable indicator.

so I would need to replace the aquasoil or convert to KH when it does eventually exhaust itself.

Correct.

But humic buffering down to pH 5 is great, I don't feel so bad about my 5.8 as much.

I wouldn't know why you would feel bad unless your pH drops under 4.5. Also be aware: even if the water has sufficient KH for the tests to work correctly, pH drip tests still have a variation of +/- 0.3-0.5 points. So let's just say your pH is roughly 6.

I'm assuming the chart you're referring to is one like this?

Yes, the classic chart. Please be aware it shows the ratios without changing one of the factors. So e.g. if you shift the CO2 up you shift pH down as well as KH. While raising KH you raise pH and lower CO2.

According to that though, if I have no KH, I can get away with half the CO2 injection I thought I needed...

You actually have to get away with no injection at all. If you let RO sit open to the air, the pH usually goes down to about 5 to 5.5 and stabilizes there.

Be careful with this chart. Better yet, don't use it! It's probably the most mis-used chart in the planted tank hobby. Your final remark is a very typical example of this.

Exactly! Most charts end at 1°KH, a few at 0.5°KH and people assume they need less CO2 below that. If you look at charts that go far enough down you will see that with a KH of 0.1 and a pH of 6 CO2 is down to only 3mg/l. But adding more CO2 below that is exactly the situation I described above: pH-crash and too high CO2-Levels for fish.

For fish, I don't know how fish react to pH changes. I assume most if not all are attuned to fixed often dramatic patterns caused by CO2/plants or, because plants are often absent in natural bodies of water, but not the decomposing parts from hanging over vegetation that have fallen into the water, CO2/microbial activity.

Ground rule for fish: Most can handle pH-swings of +/- 4.0 points provided they happen SLOWLY. So from a pH of 8.0 to 5.0 within 4-5 hours is no problem, while the same switch in less than 1 hour is 100% fatal.

 

Active soils should be looked at as a bunch of minerals that gets slowly depleted over time and as Cation Exchange Capacity, which stays pretty much stable and....exchanges cations. For instance, initially, typically H+ is exchanged for Ca+ and Mg+. Hence active soils, initially, lowers pH, KH, GH. Over time, the exchanges will become different. But initially, active soils contain a lot of H+.

"about 1-5 years"? I strongly doubt this. 1-1.5 years is more likely.

Be careful with this chart. Better yet, don't use it! It's probably the most mis-used chart in the planted tank hobby. Your final remark is a very typical example of this.

If you target 25 ppm CO2, you'll need to inject the same amount regardless if your water is KH low or high.

Ok. So keep my CO2 injection the same but make sure I aerate at night. And trust the drop checker, not the chart

 

but make sure I aerate at night

Yes.

And trust the drop checker, not the chart

I wouldn't trust the drop checker either, it's also dependent on KH.

 

I'm approaching the topic from the opposite side of ruud, obviously. I'm specialized on fishkeeping and extreme softwater parameters.

Partially. But not entirely. As I don't use the stuff myself the only thing I know is: The effect wears off with dilution by waterchanges. And going by observations of people that use it, the effects are gone after between 2 and 8 months depending on the specific product and the percentage and frequency of waterchanges.

The colour of the water has no correlation to the amounts of humic substances. It is no reliable indicator.

This is an interesting point. Is it possible to get the blackwater buffering benefits without coloring part of it then?

I wouldn't know why you would feel bad unless your pH drops under 4.5. Also be aware: even if the water has sufficient KH for the tests to work correctly, pH drip tests still have a variation of +/- 0.3-0.5 points. So let's just say your pH is roughly 6.

Cool! That's what I mainly wanted to check on. I know chasing pH isn't the point but I wanted to make sure the bits that caused that low pH weren't going to hurt the fish.

But adding more CO2 below that is exactly the situation I described above: pH-crash and too high CO2-Levels for fish.

Ground rule for fish: Most can handle pH-swings of +/- 4.0 points provided they happen SLOWLY. So from a pH of 8.0 to 5.0 within 4-5 hours is no problem, while the same switch in less than 1 hour is 100% fatal.

Yup, when I run out of buffering capacity. I'll keep an eye out but it sounds like the soil buys me time to decide which buffering route I want to take.
I imagine aerating away CO2 at night won't cause pH swings drastic enough to bother fish too much...

Thanks so much for the advice! I've learned a lot tonight

I wouldn't trust the drop checker either, it's also dependent on KH.

Oh, drop checker solutions are always 4-5 dKH solution with some bromothymol blue, so my tank water params shouldn't affect it's reading ability, just the CO2 content.

 

Is it possible to get the blackwater buffering benefits without coloring part of it then?

Not entirely without it. But here for comparison:


Homemade humic extract from catappa leaves, alder cones and rooibos tea


RO treated with storebought humic extract


and the tank water.


In the tank the water still looks more like the homemade extract, although it isn't.

Yup, when I run out of buffering capacity. I'll keep an eye out but it sounds like the soil buys me time to decide which buffering route I want to take.

Don't delay too long. You should make up your mind in time before the effects wear off significantly.

Cool! That's what I mainly wanted to check on. I know chasing pH isn't the point but I wanted to make sure the bits that caused that low pH weren't going to hurt the fish.

Keep in mind: It's the timeframe, not the amplitude.

I imagine aerating away CO2 at night won't cause pH swings drastic enough to bother fish too much...

Keep a very close eye on it. I'd turn the CO2 off overnight. But then again: I don't run CO2 at all and keep plants that get their CO2 directly from the air.

 

For your permanent aeration, do you mean a bubbler or just strong surface agitation by your filter outflow?

Bubbler is what I use. Biofilm is a blessing, except when it's covering the water surface. I keep a tiny O2 hose just below the water surface. In CO2 terms, about 10 air bubbles per second is enough to keep relatively large water surfaces clean. For my largest tank, that is obstructed by wood sticking out of the water surface, I use two of these at opposite sides.

The bubbler also help off-gassing the CO2. Most use a bubbler at night, many also permanent. Because O2 is the most important parameter in our hobby (in my opinion) I advocate day and night, regardless if you inject CO2. But with CO2 injection, off-gassing is beneficial too. Here's a nice reference, which saves me some writing:
Surface agitation & gaseous exchange in CO2 injected tanks

 

View attachment 868997
and the tank water.
View attachment 868998
In the tank the water still looks more like the homemade extract, although it isn't.

That's not bad at all! I have some store-bought extract on hand for my caridina tank, it definitely colors the water like your store-bought example but the homemade one is a lot milder. How do you measure when you've hit enough buffering with tannins?

 

How do you measure when you've hit enough buffering with tannins?

I don't. It's experience plus I want it to be dark. I add 2 liters of extract made from pure RO and 10-20 alder cones, 5-6 leaves (catappa, oak, beech, whatever I have) and 2 teabags of rooibos every week with the waterchange.
pH is around 5, which I check with a borrowed lab grade meter once every three months and the only thing I check regularly is TDS/EC, which come out between 30-40mg/l or 60-70µS/cm. That's softwater habitat focused aquatics for you.

 

I don't. It's experience plus I want it to be dark. I add 2 liters of extract made from pure RO and 10-20 alder cones, 5-6 leaves (catappa, oak, beech, whatever I have) and 2 teabags of rooibos every week with the waterchange.
pH is around 5, which I check with a borrowed lab grade meter once every three months and the only thing I check regularly is TDS/EC, which come out between 30-40mg/l or 60-70µS/cm. That's softwater habitat focused aquatics for you.
View attachment 868999

Wow, that tank looks cool! And your water is super soft, whoah. Don't think I'll be able to get mine that dark though haha.

The bubbler also help off-gassing the CO2. Most use a bubbler at night, many also permanent. Because O2 is the most important parameter in our hobby (in my opinion) I advocate day and night, regardless if you inject CO2. But with CO2 injection, off-gassing is beneficial too. Here's a nice reference, which saves me some writing:
Surface agitation & gaseous exchange in CO2 injected tanks

Yeah, I'm hoping to only off-gas at night as the tank sits next to me as I work during the day and prefer it whisper quiet. The article does mention that skimmers do a good job agitating as well, I do plan on getting one of those eventually.

 

Wow, that tank looks cool! And your water is super soft, whoah. Don't think I'll be able to get mine that dark though haha.

Thanks. And, oh, you can get your tank that dark and also that soft. But I doubt your plants will like it, though.

 

Wow, that tank looks cool! And your water is super soft, whoah. Don't think I'll be able to get mine that dark though haha.

Yeah, I'm hoping to only off-gas at night as the tank sits next to me as I work during the day and prefer it whisper quiet. The article does mention that skimmers do a good job agitating as well, I do plan on getting one of those eventually.

That's the reason I don't use air stones, but only the tube. I'm surrounded by 5 tanks in my "office". As long as the water surface is clean, running only at night is fine.

Skimmers, active soils, pH controllers, fancy lights.... we've all been there .

 

Skimmers, active soils, pH controllers, fancy lights.... we've all been there .

Nope not all of us.

 

Nope not all of us.

That's because you're a smart guy who understand plants don't belong under water.

 

Rather because I'm a technophobe Neanderthal, who avoids fads like the bubonic plague, but I let your explanation stand as legitimate.

 

Hey!

I've yet to read the whole thread so not 100% sure of what has been written already ("sorry" guys, but that's so interesting by what I've read so far that this will be my evening lecture with a good glass of wine, not even kidding ) but I thought I'd chime in since I've got quite some experience with soil.

First of all, forget about the pH drop. Basically forget everything you read about that when it comes to soil. Trust the drop checker only and use a solenoid valve. Seriously, that setup already cost a ton of money, don't try to save the 20 bucks for a solenoid.

Why do drop checkers work in soil but everything else is just a guessing game?
Well that's because drop checkers work by diffusing CO2 in the test liquid in the drop checker. It is not influenced by your fish tank water at all. Just make sure you get one with a standalone checker liquid and nothing you need to mix with your tank water.
Forget about measuring pH since soil is active and influences your KH by quite a bunch.

Rule of thumb: Halving the KH with a constant CO2 level drops the pH by 0.3 points. and with those low KH levels that's massive. If your soil lowers your KH from .2 to .1, that's already a .3 pH drop.
This is not 100% the case with soil as it also puffers the pH, but the fluctuation will be high enough to mess with your readings and setup.

That's why the drop checkers are so handy. 20ppm CO2 in the tank are 20ppm CO2 in the tank. No matter the KH or pH, which you can not reliably measure, let alone put into correlation, in a soil tank anyways.

I would also advise on remineralizing your RODI water to a KH of about 1 - 1.5. Yes that will drain your soil faster but you eliminate the dangers of a pH-crash that Mac was mentioning. Even if your soil is fully drained over time, you will still have the KH as a puffer, as the soil will stop destroying it.
If you keep your setup running as is, soil will give you a false security. It will work for months and years and you'll just think "Alright, everything fine" ... until one day it's not fine anymore.

How long the soil stays active depends on the soil and about a thousand factors. "Several years" is just advertising ... 6 months in high KH, 18 months in low KH. 24 months is already a long time for soil and if it's still active after that, you're lucky.

If by DIY system you mean anything else but pressurized CO2: Either switch to a pressurized system or use something we use here in Germany. It's called "Paffrathsche Rinne" ... I'm not sure if that even exists outside of Germany and the bordering countries. The only thing I found about this ins English is here:
https://www.reddit.com/r/PlantedTank/comments/6jfc0c
Might be worth translating this for the English fellows, what do you guys think?

CO2 driven by yeast or similar is highly dangerous in low KH setups, if not combined with the right method to dissolve it into the tank. If the temperature in your room rises by 5 degree in summer, that might already be the death of all fish.

That's my 2 cents for soil and CO2.

 

I think Gerald has ordered a CO2 system by now.

Paffrathsche Rinne .... I think it has gotten some attention in the US through this fish store

 

Hey!

I've yet to read the whole thread so not 100% sure of what has been written already ("sorry" guys, but that's so interesting by what I've read so far that this will be my evening lecture with a good glass of wine, not even kidding ) but I thought I'd chime in since I've got quite some experience with soil.

...

That's my 2 cents for soil and CO2.

Thanks for that!
I gave it some thought and I think what I will do is mark a date about 6 months ahead in my calendar to remind myself to start dosing KH at that point, maybe with baking soda or some crushed coral in my filter media. I've had good experiences so far with softwater tanks, plants, and the lack of algae and issues so that will give the tank time to mature before I start slowly moving the parameters. I had bad experiences with a hard-water tank with Seiryuu style rocks in it.
I'll definitely consider a pressurised system, the temperature swing with the yeast system is definitely a risk. I'd like to first observe how the tank responds to 1) too much CO2 with a warm room and 2) Higher water agitation via an oxygen line. I have heard of bell diffusers (Paffrathsche Rinne) in another forum used successfully actually, but it's a big thing that sits in the tank so I wasn't a huge fan. Plus I love the sight of CO2 bubbles dancing around the tank

 

Soft water makes things a bit easier. But in the end, we have a few controls to dial, and regardless how you dial them, nature finds a way.

But oftentimes, people intervene faster than nature requires. And blame the parameters.

Here's how I run bubblers. The noise you hear in the background is the air pump that serves 3 tanks with bubblers.

 

Heya!

I had bad experiences with a hard-water tank with Seiryuu style rocks in it.

Depends on how hard the water is.
If your KH is >10 and you keep CO2 at about 15ppm, the stones shouldn't harden up much.

If you push your CO2 to 30ppm and / or reach acidic territory then yes, that might be a problem.

My 35l is set up with CO2 and Seiryu rocks, no problems at all so far.
No soil though, KH is around 6 and pH is kept around 7.

In my tanks in which the KH is very low (<2) and I'm hovering around a pH of 6, stones that harden up are completely banned though.

 

Soft water makes things a bit easier. But in the end, we have a few controls to dial, and regardless how you dial them, nature finds a way.

But oftentimes, people intervene faster than nature requires. And blame the parameters.

Here's how I run bubblers. The noise you hear in the background is the air pump that serves 3 tanks with bubblers.

That is a pretty slow bubbler. And your caridina shrimp look so happy! I have a caridina shrimp tank with CO2 injection as well (although I'm running it lower), I might try the same thing as you and have a single air pump drive both my tanks at night. Thanks for the video!

In my tanks in which the KH is very low (<2) and I'm hovering around a pH of 6, stones that harden up are completely banned though.

Haha, yep, I'm tending towards soft-water these days so no more calcium stones for me


I found an interesting discovery today that might contribute to this discussion. Yesterday I added too much tannins to my shrimp tank, I was a little worried about the coloration affecting my plants. I was a little worried about my pH dropping too but the shrimp seemed extra happy. This morning, about 60% of it has cleared up: no carbon, no Purigen. I couldn't find much on it aside from this Reddit thread but it looks like aquasoil could potentially adsorbs the tannins?
Perhaps I could have IALs and other tannin sources with the buffering capabilities of those but the aquasoil would clear up the water so I can have light-hungry plants. I do have some exhausted aquasoil from my high-KH tank, can try running some experiments on that...

 

I couldn't find much on it aside from this Reddit thread but it looks like aquasoil could potentially adsorbs the tannins?

Very possible. My Soil tanks go non-colored again pretty quickly, too.
Unfortunately, soil does the same with medicine.