# Yet Another CO2 Question



## Annextro (Nov 7, 2016)

While away this weekend I got the phone call everyone dreads: several of my fish went belly up over night! Losing fish never seems to be that much of an issue for me, and my water parameters and routine are pretty constant, so to lose two in one night raises some concerns regarding the biggest change to my system. The tank is a ~37 gallon and is moderately planted, EI dosing and 90-odd watts of fluorescent lighting.

About 3 weeks ago I began using a citric acid and baking soda CO2 system using a kit purchased online. Since then I've been really struggling to dial it in and achieve the proper balance in my aquarium... The supply of CO2 is constant (2-3bps) and is on 24/7. The CO2 is injected in to the aquarium through a ceramic diffuser placed right under the intake to my canister filter where it then goes through the system and is pumped back in to the tank through the spray bar.

I have a drop checker using a 4dKH reference solution to try and monitor any changes to the pH in the tank, but it doesn't seem to fluctuate very much. The pH of our tap water is pretty well spot on 7.0, and I have only been able to achieve a drop to 6.8-6.4 (depending on the time of day) with the addition of CO2 (2-3bps, afraid to push it much further...). Now here is where the problem begins...

I have quite a few fish swimming around the tank that need their fair share of O2, and I've always run an air stone 24/7 to make sure they're satisfied. Surface agitation from the spray bar is enough to cause the duck weed to ripple and blow around the tank, as well, which some have said should be suffice.. After reading several forum posts about the use of air stones and CO2, I came to the conclusion that I was out-gassing much of the CO2 and that this was why I wasn't seeing a drop in the pH. So, I shut off the airstone. Within a few hours, most of my fish made their way to the top of the tank and began surface breathing. I then plugged the airstone back in and the fish began to go about their business as usual. The airstone was not running yesterday or last night and that leads me to believe the lack of O2(?) was the cause for the recent deaths, not an OD on CO2 as the drop checker portrays it as being at a _safe_ level. I have tried just running the airstone at night with 24/7 CO2 as suggested by others, but this didn't seem to make the fish too happy during the day.

This leaves me running over several scenarios in my head but I don't have much experience with this, so I'm turning to you guys! I need enough surface agitation to allow O2 to move back and forth, but not _too much_ to out-gas all of the CO2... Leaving the airstone off and lowering the CO2 injection rate hasn't seemed to do much as it 1: leaves the fish surface breathing, and 2: doesn't inject enough CO2 to significantly alter the drop checker reading. Is it possible then to leave the airstone running to help with the exchange of O2, and then to increase the rate of CO2 injection to make up for the amount lost due to the airstone running...? Essentially increasing the levels of both O2 and CO2 in the water? I'm interested in seeing what you guys have to say about this and if you've ever experienced something similar. Thanks in advance for any advice!


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## Reckon (Jul 25, 2012)

Fish swimming to the top of the tank is a key indicator that you have too much CO2. Checking PH is not a good way to measure the amount of CO2 that is in the tank since PH is affected by pretty much everything: rocks, plant matter, bio waste, KH, etc etc.
The best way is to use a drop checker - you want the color to be emerald green - light green. Yellow means you have too much CO2. The problem of reading the drop checker is that there is a delay from when it changes color to the amount of CO2 dissolved. Unfortunately, the best thing to do is to watch your fish and your plants day over day to make sure you get a good response from your plants but your fish don't look stressed.

If you don't want to run an air stone then I recommend turning the spray bar so the output creates a good ripple at the surface of the water. Personally I think 2-3 bubbles per second is lots in a 37 gallon tank. You don't need to aim for more. I have about 2-3 bubbles per second going into my 50 gallon and I say its a moderate amount of CO2.

If you need more help with getting gas exchange to happen at the surface I recommend the Eheim Surface Skimmer. It will ensure there is no scum at the top of the surface.


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## Annextro (Nov 7, 2016)

Reckon said:


> Fish swimming to the top of the tank is a key indicator that you have too much CO2. Checking PH is not a good way to measure the amount of CO2 that is in the tank since PH is affected by pretty much everything: rocks, plant matter, bio waste, KH, etc etc.
> The best way is to use a drop checker - you want the color to be emerald green - light green. Yellow means you have too much CO2. The problem of reading the drop checker is that there is a delay from when it changes color to the amount of CO2 dissolved. Unfortunately, the best thing to do is to watch your fish and your plants day over day to make sure you get a good response from your plants but your fish don't look stressed.
> 
> If you don't want to run an air stone then I recommend turning the spray bar so the output creates a good ripple at the surface of the water. Personally I think 2-3 bubbles per second is lots in a 37 gallon tank. You don't need to aim for more. I have about 2-3 bubbles per second going into my 50 gallon and I say its a moderate amount of CO2.
> ...


Thanks for the reply, Reckon! So I wonder then, even when I decrease the rate of CO2 injection from 2-3 down to 1bps, the change in the drop checker reading is minimal (I have checked it at all hours of the day and night, and it always stays in the lime green/emerald range..), which would lead me to believe the CO2 is in the sweet spot.. However, the plants just aren't reacting as expected. I made a post a week or two ago targeting this issue and was recommended to switch over to EI dosing and more lighting to match my CO2 injection. EI is a go and new lighting is in the works. Maybe new lights are the missing component, not the lack of CO2, though this too was debated on my previous post. Hopefully that will add a little spark to my plant growth and I can dial back the CO2 to ease the stress on the fish... I'll see how things go!


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## Reckon (Jul 25, 2012)

Annextro said:


> Thanks for the reply, Reckon! So I wonder then, even when I decrease the rate of CO2 injection from 2-3 down to 1bps, the change in the drop checker reading is minimal (I have checked it at all hours of the day and night, and it always stays in the lime green/emerald range..), which would lead me to believe the CO2 is in the sweet spot.. However, the plants just aren't reacting as expected. I made a post a week or two ago targeting this issue and was recommended to switch over to EI dosing and more lighting to match my CO2 injection. EI is a go and new lighting is in the works. Maybe new lights are the missing component, not the lack of CO2, though this too was debated on my previous post. Hopefully that will add a little spark to my plant growth and I can dial back the CO2 to ease the stress on the fish... I'll see how things go!


Well, I would take the drop checker out of the tank and see if it turns back to blue. We want to make sure the mixture within the drop checker is working right. Depending on the style of the drop checker its possible for some tank water to get into it. Otherwise, did you make your own reference fluid or did you buy it premade?

I looked at your other thread (sorry, didn't see it last week):
Since your KH is 5, this would explain why your pH doesn't drop that much by adding CO2. 
Your water temperature should not fluctuate so much. How does it go up and down by 5 degrees? You should try to keep everything as stable as possible. 
I agree with the statements made in your other thread in that the plant degeneration is probably due to lack of nutrients, ESPECIALLY if you are running CO2. You should have SOME nitrates in your water column. Aim for 30-40ppm. You don't have be very particular in measuring, those test kits aren't that reliable, but they'll give you an idea.
Clarify your lighting situation? You are currently running 6 bulbs?? I don't know if lighting is the problem if you are.


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## Annextro (Nov 7, 2016)

Reckon said:


> Well, I would take the drop checker out of the tank and see if it turns back to blue. We want to make sure the mixture within the drop checker is working right. Depending on the style of the drop checker its possible for some tank water to get into it. Otherwise, did you make your own reference fluid or did you buy it premade?
> 
> I looked at your other thread (sorry, didn't see it last week):
> Since your KH is 5, this would explain why your pH doesn't drop that much by adding CO2.
> ...


Out of the water it is in fact blue. The style of drop checker doesn't allow any tank water in, either. I made my own 4dKH solution using distilled water + baking soda.

As per the KH that would make sense, I don't know why I didn't think that one through. The temperature fluctuation I think is largely due to the lights and the fact that the glass top traps the heat in. At night, the temperature stays around ~77° and then rises to ~81° at the end of the photo period, give or take a degree or two depending on the room temp that day. Since posting that thread I have changed over from dosing liquid Seachem products to dosing a mix of dry macro and micro ferts. I haven't had the chance to take new measurements since a week ago as I'm out of town unfortunately, but I'm assuming the new ferts will raise the Nitrate levels.

For my lights, I have 2 24" sunblasters less than 5 months old. The dual 30" fixture was used, as well as the dual 24" fixture with the colormax bulbs so I'm uncertain how effective they still are.


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## troutsniffer (Dec 10, 2015)

I almost gassed fish doing this method like last summer. This is why I said enough is enough and bought reckon's paintball co2 setup a few days ago. Can you show us your bubble counter? I'm asking because some of them are unreliable. And make sure it's level. This is why I almost killed a bunch of fish, only 2 bps was coming through, but it was actually more like 4.


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## Mark Brown (Jan 21, 2017)

diy co2 really is just throwing caution to the wind imo. You can never be positive what it is coming out at because the reaction is never truly stable. So many things can alter the speed of the reaction, heat being a common one. I would also keep the surface agitation going running it. Losing some co2 is better than losing our little friends.


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## Annextro (Nov 7, 2016)

*can't seem to delete this comment for the life of me so please ignore it*


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## Annextro (Nov 7, 2016)

troutsniffer said:


> I almost gassed fish doing this method like last summer. This is why I said enough is enough and bought reckon's paintball co2 setup a few days ago. Can you show us your bubble counter? I'm asking because some of them are unreliable. And make sure it's level. This is why I almost killed a bunch of fish, only 2 bps was coming through, but it was actually more like 4.


Sorry for the late reply, I just got back to the mainland! Here's a photo of the bubble counter I'm using. It's one of the 2-in-1 bubble counter + check valves (grabbed it for around $15 from my LFS). It has been off since posting this thread so that explains the low water level and no bubbles in the picture haha. The more and more I look in to pressurized CO2 the more I wish I skipped over the DIY citric acid unit and went straight to a setup like the one you mentioned..











Mark Brown said:


> diy co2 really is just throwing caution to the wind imo. You can never be positive what it is coming out at because the reaction is never truly stable. So many things can alter the speed of the reaction, heat being a common one. I would also keep the surface agitation going running it. Losing some co2 is better than losing our little friends.


Yeah that makes sense. I'm curious how the citric acid setup vs. a yeast reactor setup compares. Like you said, the reaction is never truly stable. but a yeast reactor seems to be a lot more unpredictable in terms of when the CO2 is being produced and pumped in to the tank compared to what I've seen with the citric acid units. Either way, a pressurized CO2 unit seems to be in my near future. I'm going to start from square 1 with my citric acid system and bubbler situation and slowly work my way up while I start planning and looking for a pressurized system.


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## troutsniffer (Dec 10, 2015)

Well the main problem is the DIY citric acid combo has no solenoid, so you either have to turn it on manually on and off, or you're going to increase the chance of gassing your fish or causing a ph crash. If you want to stick with DIY citric acid, you might want to consider buying a solenoid for it.


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## Annextro (Nov 7, 2016)

And so I figured. At this point I think I'm going to plan out a pressurized system... Search the couch for some change to put towards it and maybe utilize a solenoid in the meantime while I try figuring it all out.


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## Mark Brown (Jan 21, 2017)

pressurized isn't so bad when you get into it. Just troll the forum till someone is letting one go, I have seen some smoking deals come around. That and when you do get it all dialed in you know exactly what you are getting.

Personally I bought a drop checker then promptly threw it in the garbage. They can be a little misleading depending on placement and solution. I feel personally (I know there is a lot of debate on this) I don't care what concentration my water is at as long as my plants are healthy and my fish are happy I'm happy. That being said I also stopped using co2 for the time being because I need to build a reactor to get away from the 7up water experience of poorly chopped up bubbles in my return water column.

Best of luck to you to be certain. You will find that sweet spot we all chase!


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## Annextro (Nov 7, 2016)

Cheers, Mark!


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## AquaSox (Jun 9, 2010)

It is hard to believe DIY would ever produce enough CO2 to endanger your fish. I think you might be right OP that it an O2 (DO) issue. The water temperature fluctuation might be a problem. Try lowering your water temperature a bit...Tropica website recommends between 22-24 C and 75 F is the upper limit of that...I personally found that my plants grow better within that temperature range and the cooler the water, the higher the concentration of dissolved oxygen.

Lots of people use drop checkers....I know Tom Barr (EI founder) has been critical of them. Seems that he favors using a pH probe monitoring coupled with kH measurements.....not 100% accurate but drop checkers have a lag time and you can't really tell how high your CO2 is...only that it is "too high". Also Tropica recommends using pH and kH charts as well.


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