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Discussion Starter · #1 ·
I have a 75G tank that I set up about 2 weeks ago. I am running Fluval 407 filter, a bubble curtain, a power head to help circulation and injecting CO2 with a diffuser. I have been adjusting the CO2 slowly every day to try and dial it in, but no matter how much I inject, the drop checkers aren't turning any greener/lighter. Right now, they are a dark green and im counting 1-2 bubbles/sec. I have two drop checkers in the tank just to help me see if CO2 is reaching different areas better.

At this point my plants have been in the tank for a a week and a half and a lot of them are melting/dying off. My PH is rising. I removed some dead plants material but I am concerned about the CO2. I turned it up last night and count 3-4 bubbles per second which seems like a lot to me. Am I going in the right direction here?

For information, I buried root tabs, and am fertilizing with flourish and flourish trace alternating 2-3X/week.

Thank you in advance!
 

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To get good CO2 saturation in a 75g, you will likely have an uncountably high rate of bubbles per second (75 is the point at which a flow meter becomes helpful, if not almost essential for really consistent co2).

Not all bubbles are created equally (and no two counters count them equivalently), so no one can give you a number, but it sounds like you need a lot more.
 

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Discussion Starter · #3 ·
To get good CO2 saturation in a 75g, you will likely have an uncountably high rate of bubbles per second (75 is the point at which a flow meter becomes helpful, if not almost essential for really consistent co2).

Not all bubbles are created equally (and no two counters count them equivalently), so no one can give you a number, but it sounds like you need a lot more.
Really? All this research and this is the first time I've been told this. Thank you so much! Are all flow meters created equally? :)
 

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I agree with @EmotionalFescue, that is not nearly enough co2. When I ran co2 on my 75, it was not possible to count bubbles with as much as you need to put in. You need to measure differently. Drop checkers are ok, but not super accurate. Ph drop is the best way. Get a good ph pen and test right before co2 comes on and compare that with the ph at it's lowest during the day. You want around a 1 point drop. The fact that you say your ph is rising, is not a good sign. It should never rise, unless you stop adding co2. Also, are you running the bubble curtain during the day? That will offgas a lot of co2 as well.
 

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Discussion Starter · #6 ·
I was probably misunderstood, but I thought a bubbler was helpful to the CO2. When should I turn it on and let it run in comparison the the CO2? I got it mostly for surface agitation as I had a lot of film on the surface. I'm not sure what a Ph Pen is.. But I can use my test kit.
 

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Really? All this research and this is the first time I've been told this. Thank you so much! Are all flow meters created equally? :)
They are not, unfortunately... the ones that work well for us have flow ranges from 0-100ccm (or 0-0.1 lpm), and aren't the most common you'll find used. You can get a Dwyer brand meter new off the shelf in that range. All of my flow meters were purchased used off of ebay. Here's one that is lab grade and right in the zone you need (0-51ccm, which would cover you well; I run 33ccm in my 120g) but priced kind of high: ebay listing number 304196099765. Here's another one (I have one of these): ebay listing number 182673197211. It has a 0-62ccm flow range, but the valve on it really only works as a shutoff (not precise enough to control flow well in that range). You could probably use your existing needle valve that feeds into your bubble counter though.

Lotta ins, lotta outs, lotta what-have-yous when it comes to flow meters.
 

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Discussion Starter · #8 ·
They are not, unfortunately... the ones that work well for us have flow ranges from 0-100ccm (or 0-0.1 lpm), and aren't the most common you'll find used. You can get a Dwyer brand meter new off the shelf in that range. All of my flow meters were purchased used off of ebay. Here's one that is lab grade and right in the zone you need (0-51ccm, which would cover you well; I run 33ccm in my 120g) but priced kind of high: ebay listing number 304196099765. Here's another one (I have one of these): ebay listing number 182673197211. It has a 0-62ccm flow range, but the valve on it really only works as a shutoff (not precise enough to control flow well in that range). You could probably use your existing needle valve that feeds into your bubble counter though.

Lotta ins, lotta outs, lotta what-have-yous when it comes to flow meters.
Thank you for that. Is there any way to really find a good starting point of how much flow to run? Im sure it varies with how many plants I have, what kind of plants I have, etc...
 

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I was probably misunderstood, but I thought a bubbler was helpful to the CO2. When should I turn it on and let it run in comparison the the CO2? I got it mostly for surface agitation as I had a lot of film on the surface. I'm not sure what a Ph Pen is.. But I can use my test kit.
Good gas exchange is important for running co2. If you have surface film and little agitation, you'll have your co2 saturation increasing throughout the day when what you want is for it to reach a certain point and stay there for your entire light period. Surface skimming and agitation allow you to set your co2 flow rate to reach a target that you can hold throughout your lighting period. Without them, you can get into dangerous-for-your-fish territory pretty easily. So, an air stone can be helpful, but maybe not running constantly throughout the lighting period. This is where pH monitoring comes in. In order to dial in your co2, you really want to be able to monitor your pH throughout the day for a little while. Then you can figure out how long before lights on to turn on the co2, what flow rate you need, how often and for how long to turn on your airstone, etc. Figuring all of that out with a drop checker is incredibly difficult because it has such a delay... Your co2 at lights on could be perfect, but your drop checker won't be lime green until two hours later. If you turn the co2 up in the morning while it's still kinda blue, it's then yellow mid afternoon, etc...

Thank you for that. Is there any way to really find a good starting point of how much flow to run? Im sure it varies with how many plants I have, what kind of plants I have, etc...
For a tank that size, I would recommend starting with something in the 15-20ccm range (note that I'm talking in terms of ccm of air, which corresponds to slightly less co2, but the scales are usually in terms of air, if you can find them at all). I run 18ccm (air) in an 80g tank with a sump to get a 1pt pH drop. That's using the Brooks meter from the second listing I pointed you to. That meter's great because it has a ccm air scale built in. I think I got mine for an offer of $50 fwiw.
 

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I was probably misunderstood, but I thought a bubbler was helpful to the CO2. When should I turn it on and let it run in comparison the the CO2? I got it mostly for surface agitation as I had a lot of film on the surface. I'm not sure what a Ph Pen is.. But I can use my test kit.
Surface agitation is good, as it allows oxygen in, but anything that breaks the surface will release co2. Powerheads are the best way to get agitation without breaking the surface, and you already have one. Just point it towards the top of the tank and get a good ripple going across the surface.
 

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Discussion Starter · #11 ·
So surface agitation without breaking the surface will help get rid of the surface film? This will also allow oxygen in but trap the CO2 in the water as well. Am i correct with this?

Good gas exchange is important for running co2. If you have surface film and little agitation, you'll have your co2 saturation increasing throughout the day when what you want is for it to reach a certain point and stay there for your entire light period. Surface skimming and agitation allow you to set your co2 flow rate to reach a target that you can hold throughout your lighting period. Without them, you can get into dangerous-for-your-fish territory pretty easily. So, an air stone can be helpful, but maybe not running constantly throughout the lighting period. This is where pH monitoring comes in. In order to dial in your co2, you really want to be able to monitor your pH throughout the day for a little while. Then you can figure out how long before lights on to turn on the co2, what flow rate you need, how often and for how long to turn on your airstone, etc. Figuring all of that out with a drop checker is incredibly difficult because it has such a delay... Your co2 at lights on could be perfect, but your drop checker won't be lime green until two hours later. If you turn the co2 up in the morning while it's still kinda blue, it's then yellow mid afternoon, etc...



For a tank that size, I would recommend starting with something in the 15-20ccm range (note that I'm talking in terms of ccm of air, which corresponds to slightly less co2, but the scales are usually in terms of air, if you can find them at all). I run 18ccm (air) in an 80g tank with a sump to get a 1pt pH drop. That's using the Brooks meter from the second listing I pointed you to. That meter's great because it has a ccm air scale built in. I think I got mine for an offer of $50 fwiw.
So for example, I should test my PH before the CO2 turns on. And then periodically check the Ph throughout the day. Say every 30- 60 minutes. I want the Ph to drop 1 value while the light is on and ideally get that drop by the time the light turns on for optimum efficiency. If it drops more than 1, then I have too much CO2. Then when the lights are off, while plants are not photosynthesizing, I can turn the air on and get oxygen in the tank and not have to worry about CO2 escaping because the plants arent using it anyway. Is this correct?

Im still a little confused at how to figure out flow rate and how to make sure CO2 is saturating the whole tank. Right now it seems like the plants on the opposite side of the tank from the diffuser are doing much better than the plants close to the diffuser.
 

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So surface agitation without breaking the surface will help get rid of the surface film? This will also allow oxygen in but trap the CO2 in the water as well. Am i correct with this?
Yes it will help. A surface skimmer also helps a lot. I'm not sure if your filter came with one or not but it's a good thing to have. You may also need to add a second powerhead if you still have areas with surface film. And that is correct. If you think about a bottle of soda, it has a ton of dissolved co2 in it. And if you agitate it, all of the co2 comes out. But the surface ripples don't reallly agitate the water, but still help to promote oxygen exchange.

So for example, I should test my PH before the CO2 turns on. And then periodically check the Ph throughout the day. Say every 30- 60 minutes. I want the Ph to drop 1 value while the light is on and ideally get that drop by the time the light turns on for optimum efficiency. If it drops more than 1, then I have too much CO2. Then when the lights are off, while plants are not photosynthesizing, I can turn the air on and get oxygen in the tank and not have to worry about CO2 escaping because the plants arent using it anyway. Is this correct?

Im still a little confused at how to figure out flow rate and how to make sure CO2 is saturating the whole tank. Right now it seems like the plants on the opposite side of the tank from the diffuser are doing much better than the plants close to the diffuser.
Yes, that is the gist of it. You may want to take a cupful of water out of your tank and let it set for 24-48 hours, and then test that. Even with a bubbler, some co2 will probably stay in the tank overnight. But if you let the cup sit for a while, all of the co2 will escape, and you will get a more accurate starting point. Then just test your water periodically throughout the day and see how much it drops. I would make drastic changes or multiple changes. Do it slowly and a little bit over time, with good observation. You really have to tweak it for a while to get it to where you want it to be. But ideally, yes, you do want to get close to that 1 point drop by the time the lights come on, and stay there throughout the photo period. More than 1 point is not necessarily too much. Some do go higher, but 1 point should be good. Keep an eye on your fish during this time, just to make sure you don't go too far. They should be able to handle more than a full point drop though, so you have some room for error. And if you do see them at the top, don't worry too much. I've had times where they were gasping at the top the whole day, because of a malfunction when i wasn't home, and they all recovered quickly once I got them so more oxygen. If you see it, just turn on your bubbler for a little bit and they will be fine. And yes you are correct. The bubbler is ok at night, because the plants only need the co2 while the lights are on.

As far as the flow rate goes, it can be helpful to have a flowmeter. It makes it easier to see how much you are changing it, but it's not critical. I've never used one before. The ph change will tell you how much is actually dissolved in the water and that's what matters the most. Just be slow and methodical with your changes and eventually you will dial it in. You might also want to play around with the location of your diffuser, and your powerhead to see what works best.
 

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So for example, I should test my PH before the CO2 turns on. And then periodically check the Ph throughout the day. Say every 30- 60 minutes. I want the Ph to drop 1 value while the light is on and ideally get that drop by the time the light turns on for optimum efficiency. If it drops more than 1, then I have too much CO2. Then when the lights are off, while plants are not photosynthesizing, I can turn the air on and get oxygen in the tank and not have to worry about CO2 escaping because the plants arent using it anyway. Is this correct?

Im still a little confused at how to figure out flow rate and how to make sure CO2 is saturating the whole tank. Right now it seems like the plants on the opposite side of the tank from the diffuser are doing much better than the plants close to the diffuser.
Yes - more or less. The baseline pH is taken from degassed tank water, not what you're starting out in the morning. So you'll want to pull some tank water out and let it sit for a while (~36hrs), then measure its pH. That's your baseline. Your target drop is measured against that. 1.0 is a good target, but many shoot for more. I have a 1.2 drop in one of my tanks and 1.0 in another. The former is higher light with a lot of stems, the latter has a lot of crypts and swords etc. Some folks go as high as 1.4-1.5.

Once your light turns off you don't need the co2 and can use your air stone. Some people also use an air stone periodically during their light period... that could be good if you really want to push the envelope with high light. When I'm dialing in co2 I use a pH monitor so I can easily pop over and check out where things are at throughout the day. If you're going to buy a pH pen anyway, it might be worth looking into something like a Milwaukee monitor (that's what I use).

Flow rate is just something you'll have to dial in after starting... somewhere. Again, having a reliable way to monitor your pH really helps here. Also, for what it's worth, I turn my co2 on a solid three hours before the lights, where most folks recommend much less. I've found you're still climbing the co2 saturation curve before that point and have largely leveled off after it. Your mileage may vary, of course. Have I mentioned how important it is to have a reliable way to monitor your pH during this process???

As for even distribution, that's a function of your water flow in the tank and your method for getting co2 into the water. In my experience, you're going to have the easiest time nailing co2 with (1) a reactor, (2) a spraybar, and (3) a skimmer (or overflow->sump). That's not to say you can't have a good co2 setup without those things, but it would be easier to get it right with them.
 

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Discussion Starter · #14 ·
I want to go with a reactor. I like the idea of a spray bar. Not sure about the sump though, any real benefits of it?

I adjusted the CO2 to turn on 2 hours before the light. They both run for 7 hours. I also set the bubbler to run when the CO2 is off. I turned the CO2 way up when I got home and the drop checkers actually turned like green!!! Thank you so much for all your help. I'm pulling some water out to check after 36 hours and I'll start tracking Everything.

My light has an option to be white or purple... Does it matter which one I use?
 

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Sorry, I didn't mean to suggest you should switch to a sump, just meant to say that surface skimming is important. If you use a canister, you can get that from a separate skimmer or one integrated into your filter intake. If you have a sump, you have skimming by default.
 

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Discussion Starter · #16 ·
Sorry, I didn't mean to suggest you should switch to a sump, just meant to say that surface skimming is important. If you use a canister, you can get that from a separate skimmer or one integrated into your filter intake. If you have a sump, you have skimming by default.
How does a surface skimmer help with CO2? If I have surface agitation, isn't that what the goal is? In my current situation, my power head and my outflow provide the agitation, and Ill have more with the spray bar.
 

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How does a surface skimmer help with CO2? If I have surface agitation, isn't that what the goal is? In my current situation, my power head and my outflow provide the agitation, and Ill have more with the spray bar.
Surface film acts as a membrane that inhibits gas exchange. With good agitation you will have a portion of your surface clear of film - which will be helpful and good - but you would be better off with agitation and skimming together.
 

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That makes sense. So if I don't see any film as is, a skimmer is unnecessary?
I would be surprised if you were able to avoid surface film long term without some sort of mechanical intervention.
 
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