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Hello everyone

After following a lot of posts here at FP concerning CO2 injection and various anecdotal accounts of methods used I thought I'd "change up" the way I've been doing something for sometime (2 or so years)...

That is: leaving the CO2 going overnight where as up till this point I have always disconnected it at "lights out". I’ve always done this on the simple grounds of “no light = no photosynthesis = plants only respiring = plants producing CO2 without consuming any”

One of the main arguments I've heard for doing this was to prevent pH swings overnight.

To help with everyone's understanding of my set-up:
- DIY Yeast/Sugar mix, delivered by an airstone
- "Low light" flouro set-up
- Filtration provided by a Fluval 404 (40 Gal tank), with the output _just_ below surface level to provide near maximum surface agitation (yes, yes, I know, but bear with me on this point and I'll explain in a second)
- Ferts via "Aqua Master Plant Food" drops (2.1 ml daily)
- 5 Gal water change twice each week (tap water pH = 7.2 consistently during period)
- Nitrate = 10 ppm (consistently over the period of this little test (tested whenever testing pH))
- Hardness is unknown (sorry have never had a test kit for that)
- No buffers/pH modifying chemicals have ever been used

How I tested:
- pH tested immediately prior to turning lights on in the morning and immediately prior to turning them off at night
- for each day/night test, two readings were taken to ensure accuracy using an "Aquarium Pharmaceuticals" test kit


Results:

Event/Test pH
=======================================
Day 0 Water change n/a
Day 0 PM 6.4
Day 1 AM 6.4-6.6*
Day 1 PM 6.4
Day 2 AM 6.4-6.6
Day 2 PM 6.4
Day 3 AM 6.4-6.6
Day 3 Water change n/a
Day 3 PM 6.4
Day 4 AM 6.4-6.6
Day 4 PM 6.4
Day 5 AM 6.4-6.6
Day 5 PM 6.4
Day 5 CO2 Left connected n/a
Day 6 AM 6.0

* where 6.4-6.6 is indicated, the test result, to my eyes, was between the two

Notes:
Today is day 6, so will test tonight, leave the CO2 connected again overnight, and then re-test in the morning. If it’s a 6 again I’ll be going back to disconnecting at night (figure a 0.1-0.2 swing up is better than a 0.4 swing down in pH). Will add results to this thread tomorrow.

I go the active surface agitation route after playing with various ways in the past. Obviously in a low-light set-up I’ve never had heavy pearling owing to both light levels and species selection, but those that have “pearled” to any degree seemed to do the same for me whether I had a lot of surface agitation or not, so I thought "what the heck". Looking into this has turned up such things as this]http://www.thekrib.com/Plants/CO2/co2-loss.html[/link]. The fish have always been my primary concern in my tank either way, so I just left it as surface agitation. On a (somewhat) related point, I’ve always been a strong believer in lots of water movement, and [link=this would seem to indicate that it could be beneficial for plants. Prior to changing over to the Fluval a couple months back, both water movement and the bulk of agitation was handled by a separate powerhead (filtration at that point being the domain of a HOTB Dynaflo 3).

Either way, it sure seems the agitation isn’t hampering the retention of CO2 _too_ much presuming the 0.4 drop in pH was indeed caused by the CO2 been left on overnight.



Ok, so what’s everyone’s thoughts/comments/advice/abuse on this matter?

Dex




Last edited by dextroze at 23-Oct-2004 20:26

Pretty neat.

The Amazon Nut...

Hi,
Interesting research, and comments.

I've read that CO2 saturation at equilibration is 5mg/l
rather than the measured 2-3mg/l mentioned in your first
extract. I too have read and found that some circulation
within a tank is advantageous to both plants and fish.

Having said that, let's look at what is going on.
You and I have both heard from folks who turn their CO2
off with the lights. They say, rightfully so, that
at night the plants turn from producing O2 to consuming
it. They are concerned that the demand for O2 is increased
and that the fish could be stressed or killed by lack of
O2.
Some not only turn off the CO2 injection, they also turn
airstones!
Others question the sense in continued injection when
it will not be used by the plants during the night hours
so why not turn it off?


First, for one to stress the fish with lack of O2, your
CO2 saturation has to approach or exceed 30-40mg/l.
The only real way to know is to observe the fish just
before the lights are turned on. IF they are gasping
at the surface THEN the CO2 saturation is too high, and
you should take steps to lower it. Immediatly, cut
back on the rate of delivery, AND turn on an airstone.
To put fish into this situation you would need to have
the tank way over stocked, and the CO2 saturation at
30mg/l or higher with huge amounts of plants.
The tank would almost have to look like a tank in the
LFS that is for feeders and then heavily planted.

The claim that the pH changes drastically over the night
hours, may be true.. IF and only IF the KH values are
low. I've read that at a minimum the KH should be 3dGH
and preferably around a 4 or 5. If your KH is that high,
then the carbonate will buffer the acid and the pH swing
will be will within the tolerance of any fish. If the
KH is too low, then a little acid will produce a larger
swing in pH and it could stress the fish.

With a bottled CO2 system, it is easy to adjust the needle
valve on the regulator for the desired number of bubbles
per second and maintain that for the life of the tank.
To adjust the injection rate, the best way is to measure
your pH, and KH before starting injection. Then look at
the charts, and see where you are, and where you want
the saturation to be.
15mg/l is about right although many will take it much
higher. Look at what the pH will be at that point, and
then start to inject the CO2 beginning at a bubble/second.
This is a good starting point as it is easily timed.
You should (I would recommend) purchase an electronic
pH monitor such as the "Pinpoint" monitor, calibrate it,
and keep it in the tank 24/7.
After looking at where you are, and where you want to be,
take at least 24 hours to get there (for a small change). That will allow the fish to adapt to the changing
pH without stress.

If you really must turn off the CO2 at night, then the
best way is to use a solenoid, an electronic on/off valve,
so that the regulator settings remain untouched once set.
Once you go to the trouble of setting the valves correctly,
you don't want to turn them off and then turn them back
on the next day. Your chances of achieving the same setting
each time are nill.

With a DIY system, there is no control of the amount of
CO2. When the batch is first mixed it churns like heck
and produces huge amounts of CO2. As the mix ages, the
CO2 output drops off to nothing. If you attempt to regulate
the gas injection by restricting the line ( "T" valves)
then the resultant back pressure can expode the plastic
bottle at the worst, or at the least spring leaks in the
connections. This large volume of gas produced at first
causes a rapid drop in pH. Then as the mix dilutes and
the gas production drops off, the pH will rise. The
constant yoyo effect will stress the fish.
When the mix is fresh, one might need to add airstones
overnight to keep the fish unstressed, but as the mix
ages, one can do without them.

"We" try to keep the surface undisturbed so that the
CO2 will stay in the water longer. If we break the
surface with agitation, then the CO2 will attempt
to equilibrate and we will loose all that we srived
for as the gas escapes.

Circulation within the tank eliminates "dead spots" where
detritus can accumulate, hot and cold areas, and circulates
nutrients throughout the tank. "A lot" of circulation can
be a bad thing. Fish need places to "rest."
Even the zebras who love to swim in currents, have to have reduced current areas where they can rest. Ripples, as
long as they don't stir the surface into bubbles, are fine. Power heads or filter returns below the surface are fine. Again, you don't want to break the surface into bubbles. You want to maintain the surface tension to keep the water above normal saturation for the plants.

Frank


Last edited by FRANK at 24-Oct-2004 01:54

-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Hi Frank and DaFishMan,

Thanks for the responses

Yes, I've seen the worries re: O2 during the night hours of some people... and that has never really been on my radar (what with the agitation level and all)

My specific concern, however, relates to the CO2 levels in my set-up (which I know is rather unorthodox all round, but I am specifically searching for an alternative approach).

I'm not so much worried about how much O2 the plants are consuming over night, because I have a feeling the levels with the agitation will always be more than adequate for all inhabitants of the tank, both plant and animal alike. My reasoning for turning the CO2 off was that, since the plants aren't consuming it in the dark, then it will not be utilized and to some level build up (all other things been equal). With the lights out, you have the CO2 from the injection, as well as that being produced by both fish and plants.

In relation to thekrib.com data on CO2 reduction rates, my personal thinking was that for whatever the concentration of CO2, the rate of reduction, even with agitation, was taking hours. And since, unlike in that experiment, the CO2 is constantly been fed in, it to some degree is being maintained (otherwise it wouldn't be detectable at all, either when studied by people who know what they are doing, or by clueless muddlers like me observing a pH drop over night). Unless you were already at saturation point whilst the plants were consuming, then there must always surely be room for some accumulation once they stop taking it up.

Since the swing was from 6.4 at the end of the day to 6.0 come morning, something was going on that wasn't before. I'm guessing, since my light cycle is 10 hours on 14 off, that the previous mornings' readings of 6.4-6.6 represent the water sans any influence of CO2.

After reading your reply, I'm presuming the swings I've experienced, both up in the past and down over night last night must be connected to the hardness, the value of which is sadly unknown at this point. My guess, after all that you have said, is that it must be dang low, and I'm going to go out of my way to obtain a test for it within the next few days to check this. For what it's worth, the claimed total hardness of our water districts supply is 49-56 mg/L of CaCO3, that plus driftwood in the tank etc... not looking good.

Looking at the lack of a measurement of KH, I realize just how sadly lacking this little test really has been empirically speaking.

I will, for one more night, leave the CO2 attached just so I can get a reading in the AM for tomorrow. But until I know what is going on for sure, I'll only subject the fish to the ~0.1 rise over night when it's disconnected, as opposed to the 0.4 fall when I've left it on (only to have it apparently climb back up by 0.4 during the course of the following day).

I guess without knowing the KH, I have no way to confirm the CO2 levels, and since the test kit bottoms out at 6.0, I can't really even try the method outlined on thekrib.com to ascertain the pH at which the CO2 content would be 10-20 ppm.

re: the aging of DIY mixes - I find the mixes I make last about 12-14 days (or did), now I change them out every weekend just to pre-empt this (the change was due today, but not wishing to mess with the figures, I'll let it run an extra day or two, and will put off the scheduled water change an extra day too)... The last CO2 mix change was the day before those shown in my goofy little table (the day prior to Day 0, which works out as been Sunday, the 17th). Since my water does seem to be showing any change in CO2 dramatically in the pH readings, I'm presuming delivery has been more or less consistent (otherwise the pH would have been much lower on Days 0/1 and would have steadying climbed closer to the 6.6 mark (maybe, *shrug*))

I know DIY is unpredictable and less than ideal. Indeed it could be argued that with my set-up it adds little benefit anyway. But I'm thinking (since the first 5 days figures were consistent, and since the 0.4 drop happened overnight when the plants weren't consuming CO2), that on a standard day the plants must be getting something out of it for the difference to be 6.0 when "loaded" and 6.4 come the end of the day.

For what it's worth for now without the KH being known, I will still do tomorrow's figures, and the following morning's after going back to disconnecting at night just to round this out. Following that, if the pH is back to it's 6.4-6.6 AM level, and 6.4 PM level at the point I get to test the hardness, I'll just presume it is the same as it was for during this weeks figures. Until all factors are known, I guess I still haven't really been able to ascertain much at all beyond the fact a swing is happening.

If anyone else out there feels like sharing there AM vs. PM figures for one morning/night I'd be much obliged (just to get an idea of what I ideally should be seeing).

Sorry I've rambled so much here, has been a long day and my thoughts are disorganised lol

Thanks again, Frank, for taking the time to read my rather flawed little notes and for being so helpful in your reply

Thanks also to DaFishMan for the support

Dex




Last edited by dextroze at 24-Oct-2004 09:53

Hi Dex,
Well in rereading my reply it was a somewhat feble attempt
very late in the night. I wish Da Fish Man had replied
publicly as I'd have been interested in his comments as
well.

"I'm not so much worried about how much O2 the plants are consuming over night, because I have a feeling the levels with the agitation will always be more than adequate for all inhabitants of the tank, both plant and animal alike. My reasoning for turning the CO2 off was that, since the plants aren't consuming it in the dark, then it will not be utilized and to some level build up (all other things been equal). With the lights out, you have the CO2 from the injection, as well as that being produced by both fish and plants."

If you turn off the CO2 with the lights, then the level
of saturation within the tank will decrease towards the
normal equlibrium of 5 (or your figures of 2-3) mg/l.
Without any solid facts, I personally would say that
it would drop off exponentially and that come morning
for all practical purposes, when you turn the CO2 back
on, you would be starting again at ground zero.

I'm of the opinion that it should be left on. You are
not "wasting" the CO2, you are "maintaining" the level
of saturation throughout the 24 hour period. It's kinda
like running the heat, during the winter, or the A/c in
the summer. If you turn either on or off completely, you
consume more energy returning the home to a comfort level
than if you left it set at some temperature during your
absence, and just "nudged" it on return. In this case,
you are wasting alot of CO2 bringing the level back up
to where you want it, instead of just maintaining.

"After reading your reply, I'm presuming the swings I've experienced, both up in the past and down over night last night must be connected to the hardness, the value of which is sadly unknown at this point. My guess, after all that you have said, is that it must be dang low, and I'm going to go out of my way to obtain a test for it within the next few days to check this. For what it's worth, the claimed total hardness of our water districts supply is 49-56 mg/L of CaCO3, that plus driftwood in the tank etc... not looking good."

Excessive change in pH between lights on, and lights off,
are normal with low KH values. The KH will buffer the
swing and molify it. Anyone who is injecting CO2 must
know the KH of their water. To determine the CO2 saturation
you have to plot pH vs KH and the result is the saturation.
Seasoned driftwood I seriously doubt will lower the pH
that much. After a while in the tank, a "rind" of
weathering and bacteria builds up on the surface of
the wood and that hinders the release of tannic acid.

Initially I believe drifwood will make a difference,
again depending upon the KH, of a few tenths of a point
on the pH of a tank. Perhaps even a whole point.
But over time as the tannins leach out, that effect
drops off.

Between light cycles, my pH shifts about .2 to .3 and the
fish suffer no ill effects. I have not really looked at
the values since that first week when I started bottled
CO2 injection years ago. I glance at the pH monitor
every time I enter the room, and as long as the
readings fall within "normal" I know everything
is alright. If something is "off" the readings trip
a "bell" in my mind and I stop and really look at the
gauges and settings.

However, I will note the values for the next few
days, chart them for you, and give you a weeks worth
of readings so you can see what is going on in my tank.

"re: the aging of DIY mixes - I find the mixes I make last about 12-14 days (or did), now I change them out every weekend just to pre-empt this (the change was due today, but not wishing to mess with the figures, I'll let it run an extra day or two, and will put off the scheduled water change an extra day too)... The last CO2 mix change was the day before those shown in my goofy little table (the day prior to Day 0, which works out as been Sunday, the 17th). Since my water does seem to be showing any change in CO2 dramatically in the pH readings, I'm presuming delivery has been more or less consistent (otherwise the pH would have been much lower on Days 0/1 and would have steadying climbed closer to the 6.6 mark (maybe, *shrug*))"

When I ran DIY CO2, I watched the rate of bubbling that
the gas produced from the hose in the aquarium. When it
dropped off, and the pH rose to the point where I was
nearing the "edges" of acceptable saturation, I would
connect a fresh bottle of mix. But, again, you need
the KH of the water to plot it all out.

Frankly, I was amazed at Plant Brain's comment that he'd
run DIY CO2 in a tank that large. He's the only person
I've read about that does that. Everthing I've read says
that 30 gallons is about as large as one wants to go in
DIY CO2 injection.
A tank that large must take at least 2 and possibly
more bottles in series, and several waiting on the
side, and trememdous dedication, to maintain a
CONSISTANT flow of CO2. Frankly, it sounds like it
borders on "work" instead of a hobby. I admire his
efforts.

Let's continue...
Frank



Last edited by FRANK at 24-Oct-2004 10:38

Last edited by FRANK at 24-Oct-2004 10:42

Last edited by FRANK at 24-Oct-2004 14:30

-->>> The Confidence of Amateurs, is the Envy of Professionals <<<--

Hi Frank

Thanks for replying again.

It's still 30 mins till lights on here, but I just _had_ to test hehehe... Sure enough it's a 6.0 (or at least a 6.0 on the card, I guess it could be lower, but we'll work with what we've got).

Just in reply:

"Without any solid facts, I personally would say that
it would drop off exponentially and that come morning
for all practical purposes, when you turn the CO2 back
on, you would be starting again at ground zero."

...

"In this case,
you are wasting alot of CO2 bringing the level back up
to where you want it, instead of just maintaining."

I'd presume that owing to the nature of gases etc that yes, it would decrease rapidly at first and then begin to slow as it approached equilibrium. And your point about starting at zero again has always been my main concern with leaving it off over night, I know it will take time to build up in the water and that time is all but wasted if it represents and hour or two out of a 10 hour window of opportunity to get CO2 into the plants. Going by those figures posted on thekrib.com, it would be fair to assume that after 14 hours of agitation, that it would be, like you have said, effectively zero.

"Anyone who is injecting CO2 must
know the KH of their water. To determine the CO2 saturation
you have to plot pH vs KH and the result is the saturation."

This is where I have let myself down I think, by neglecting chasing the KH up sooner. I cant help but feeling the more I read about this that neglecting this measure has made my progress over the last two years rather hit and miss. If I _knew_ my CO2 concentrations for the course of the day, I would be in a far better position to judge just how much is being utilized in my set-up. It would enable me to come closer to quantifying the benefits rather than just saying "oh look, them there green things are growing better with this stuff pumping in". As my tank, by it's nature, develops rather slow, it would be nice to know the limits I could push to speed things up from time to time (half of my approach is trying to balance strong and healthy growth, with a reduction in maintenance, if I could fine tune things a bit better, then when I need to speed things up for establishment purposes etc it would be nice to know the upper end of how far I can push it).

So far as the role of the driftwood in acidifying/softening the water, I guess it's hard to say in a mature tank. Most likely at first the tannins played a more significant role as you said, and then as their influence diminished, the natural maturity of the tank has being increasingly playing a hand in keeping it acid/soft (I'm guessing at this though totally lol)

" Between light cycles, my pH shifts about .2 to .3 and the
fish suffer no ill effects."

I think, all up, I've overreacted to the 0.4 drop, I do want to get my hands on a more accurate pH test though, just to confirm whether it definitely is 6.0 in the morning, or whether it's something lower that my kit just cant accurately measure. Thanks for the offer to record your values for me, so long as it isn't too much of an imposition, I would be mighty grateful for it

With the "home-brew" DIY petering out towards the end of a mix: that concerned my early on in things, and that's why now I always try and pre-empt the "ramping down" at the end by getting in first with a new mix. I guess I will have a little more latitude there once I can track my KH, but knowing me and my slight OCD leanings, I'll still end up swapping the mix out ahead of time "just to be sure"

Another point I'd like some thoughts on, is the mention on http://www.thekrib.com/Plants/CO2/co2-loss.html about the "CO2 rich layer above water". I seem to remember I saw mentions of this somewhere else when I was first investigating CO2. I wonder how much this would actually effect the diffusion from water to air? Indeed, how much doe that play a part in the effects of calmer water at the surface in CO2 saturation (ignoring breaking of the water surface for a second, just presuming it was dead flat but still moving)? Which links back to the agitation question. I know full well that gas exchange and diffusion, both into and out of the water is accelerated when the surface tension is being broken... but... When it comes to aeration, if the surface is been broken from water movement alone and that is upping the O2, then how would that compare, in a tank with glass lids, to having the air being supplied via pump or venturi? Surely if actual air is been pumped into the water from outside the tank, only to rise to the surface, it is then displacing a good deal of whatever gases are present in the space above the water? It would be interesting to compare the rate at which CO2 is being depleted from heavy surface agitation alone (with the CO2 layer present on the surface), to when you are supplying aeration from the atmosphere outside the tank and thereby decreasing the concentration of atmospheric CO2 in contact with the water's surface.

Food for thought

Until next time,
Dex

Sorry If I'm repeating what Frank said (I didn't read his whole posts), but in terms of DIY Co2, usually you can keep it running 24/7 especially because as you saw, sometimes the production of Co2 needs to catch up during the evening (as one isn't getting as much Co2 as pressurized Co2). In terms of ph, most ph changes are not going to hurt fish, unless you have certain species that are particularly ph sensitive. Most of the time that ph is a concerns is with concomittant problems, i.e. Ammonia being less toxic at acidic ph, but toxic at alkaline, etc.

For best results, however, try to have a kh of 3 or above (although my shrimp tank routinely is below this and is fine).

In terms of DIY Co2 for larger tanks -- there are indeed folks that run multiple bottles. However, if you add a teaspoon of protein powder, teaspoon of molasses, and a half a teaspoon of yeast nutrient (ammonium sulfate), you will find your DIY CO2 production increase many fold. It should last several weeks (use only 1 cup of sugar per liter), and when production slows, pour out all the mix except leaving the yeast that adheres to the bottom of the container -- then, add more sugar, protein powder, molasses, and yeast nutrient, and your mix will start again very quickly (do this overnight and it will be ZOOMING by morning).

Hi Piscesgirl

Thanks for the reply.

Have never heard of that mix, will have to give it a try. The only one I'd heard of was adding baking soda or whatnot to buffer the acid in the bottle down.

*puts it on his "to do list"*

Dex

Hey Dex.. On hard water and co2.

My 19* gh and 14* kh and 4.2ppm CO2 saturation last time I checked.

29 gal with hagen unit, I can't shut it off but wouldn't try like Frank said I don't want a bottle explosion !
My fish are ok and due to the very high gh and kh my ph doesn't even budge.. I've compared to my non co2 tanks and ph, gh, kh all constant. The low co2 saturation in my tank still makes a difference though
DaFish

The Amazon Nut...

Thanks the DaFishMan

Just an update on all this...

I bought a hardness test yesterday and just now (30 mins before lights on, with CO2 disconnected over-night) I got:

pH 6.6, KH 2, GH 6 (double tested all readings)

So as suspected the low KH must have been what is causing the swings...

What will be the best way to handle this? Sodium bicarbonate to walk the KH up to 4-5 with 24/7 CO2???

Thanks again,
Dex

Edit: had a word to Frank in chat and am going to try the bicarb


Last edited by dextroze at 26-Oct-2004 19:31

Update: have walked KH up from the 2 to _just_ (by the looks) 4 yesterday and over-night (2 separate doses of 1 heaped teaspoon bicarb each, added to tank water in a bucket and mixed before returning)... readings this AM, before "lights on" and with CO2 going overnight = pH 6.8, KH 4 (readings last night, before lights out and second dose = pH 6.6-6.8, KH 3)

Will try to get 5 with two half-teaspoon doses today and tonight, and then leave well enough alone.

MANY thanks to everyone who helped with this, especially Frank

Dex

Last edited by dextroze at 27-Oct-2004 19:52

Piscesgirl,

What is the protein powder and the yeast nutrient (ammonium sulfate), that you mentioned? Are these things I can buy in the baking section of the grocery store? Is there a generic protein powder or do I buy something like Whey powder, that is suppose to supply a lot of protein?

Thanks,

-Mike

It doesn't matter what kind of protein powder you use - just keep an eye on not using too much (sometimes that makes the mix go too crazy and bubble up too high); Soy might end up smelling better than the whey proteins, but you can even use powdered milk. I got the recipe from an article in The Journal for the Aquatic Gardeners Assoc (TAG), and was written by Tarah Nyberg. GREAT recipe - works sometimes too well! (like I mentioned with the overbubbling). I had best success with Spiruteen protein powder, but it really doesn't matter what kind.

Yeast nutrient is available at beer and wine brewing supply companies - but it is just Ammonium sulfate. Might be able to get it elsewhere as well.

Last edited by Piscesgirl at 28-Oct-2004 07:59

Since the thread is already at the top, I'll make one last note of my figures...

Got KH up to 5 mid-afternoon by adding half the bicarb I thought it would take to step from 4 - 5, pH seemed to be sitting round 6.8 over a few tests during the evening...

Now, 2 hours after lights out, I still have: KH 5, pH 6.8

Unless I get some major hiccough I'll leave this at that

Will certainly be giving that CO2 receipe a try in the near future Piscesgirl

Once again, tons of thanks all round,
Dex