'Tipping point' for Co2 usage relative to PAR? - The Planted Tank Forum
 
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post #1 of 13 (permalink) Old 10-21-2014, 05:28 PM Thread Starter
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'Tipping point' for Co2 usage relative to PAR?

Hi All,

I'm new to planted tanks and wondering if there's a good rule for when to CO2 to optimize the PAR in the tank? I realize this is a science and that cases differ, but curious if there's some good general guidance (again, new at planted tanks).

Thanks in advance
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post #2 of 13 (permalink) Old 10-21-2014, 05:36 PM
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Start with a low amount then increase gradually everyday. The max is when your fish start to gasp for air meaning that you now have too much C02. From there you dial back down. This must be done when you can observe the fish because they can end up dead.


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post #3 of 13 (permalink) Old 10-21-2014, 05:44 PM Thread Starter
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Thank you. I was actually approaching this from the opposite perspective. I'm running a 65 gallon with moderate PAR (I think) and no CO2. I'm switching tanks to one more conducive to plant growth (shorter), though I'd actually rather keep it low-tech for the near future.

So is there a point at which my PAR will become too much and it will prohibit plant health and growth? At what point does PAR become 'too much' without an added CO2 supply?
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post #4 of 13 (permalink) Old 10-21-2014, 06:03 PM
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Originally Posted by aggressor09 View Post
Thank you. I was actually approaching this from the opposite perspective. I'm running a 65 gallon with moderate PAR (I think) and no CO2. I'm switching tanks to one more conducive to plant growth (shorter), though I'd actually rather keep it low-tech for the near future.

So is there a point at which my PAR will become too much and it will prohibit plant health and growth? At what point does PAR become 'too much' without an added CO2 supply?
The quick answer is when you have so much light the algae starts growing better than the plants. That is why we add co2, so the plants grow faster and limit the alga's ability to grow. In almost every situation involving a non-co2 setup, an aquatic plant's growth will be limited by the amount of co2 it has access to, not the light.

Too many variables to calculate any sort of reasonable point where this kicks in.

Plant type, plant growth, amount of plants, bioload, substrate, fertilization (substrate or otherwise), light intensity, light duration, water chemistry...etc. All will play a role in this calculation.

It has been my experience that if you are wondering if you have to much light, you probably do. When I had my 90 gallon setup it was a stable low light setup. Things where growing and I had minimal algae. I added Co2 to this tank and the plants went insane (same low light). This tells me that co2 was my limiting factor, not the light. For grins, after I had co2, I doubled the lights. My plants didn't grow much faster, but my algae did. Not sure if that really answers your question...I guess my point is that lack of co2 is most likely already your limiting factor...adding more light isn't likely to speed up anything, but problems.
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post #5 of 13 (permalink) Old 10-21-2014, 06:14 PM Thread Starter
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Originally Posted by Daximus View Post
The quick answer is when you have so much light the algae starts growing better than the plants. That is why we add co2, so the plants grow faster and limit the alga's ability to grow. In almost every situation involving a non-co2 setup, an aquatic plant's growth will be limited by the amount of co2 it has access to, not the light.

Too many variables to calculate any sort of reasonable point where this kicks in.

Plant type, plant growth, amount of plants, bioload, substrate, fertilization (substrate or otherwise), light intensity, light duration, water chemistry...etc. All will play a role in this calculation.

It has been my experience that if you are wondering if you have to much light, you probably do. When I had my 90 gallon setup it was a stable low light setup. Things where growing and I had minimal algae. I added Co2 to this tank and the plants went insane (same low light). This tells me that co2 was my limiting factor, not the light. For grins, after I had co2, I doubled the lights. My plants didn't grow much faster, but my algae did. Not sure if that really answers your question...I guess my point is that lack of co2 is most likely already your limiting factor...adding more light isn't likely to speed up anything, but problems.

This is extremely helpful. Thank you.

For context, I have a 65 gallon now and am going to move the whole operation to a 75 gallon (same width but shorter and longer). I'm trying to determine what/how many lights to use, and what will be overkill before needing the addition of CO2.

One of my main concerns is that the plants aren't getting enough of what they need--my nitrate levels are very low and I've read (albeit sometimes contentious) information on optimum nitrate levels for plant growth. Is this something I should worry about, or just focus on algae growth or lack thereof? Again, just starting to assemble the pieces behind the science of aquatic plants...Thanks
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post #6 of 13 (permalink) Old 10-21-2014, 07:58 PM
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Here is a very good article on CO2 and light. It explains a lot of this. It also shows how much CO2 alone will stimulate growth.

CO2, light and growth of aquatic plants.
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post #7 of 13 (permalink) Old 10-22-2014, 02:13 AM Thread Starter
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Here is a very good article on CO2 and light. It explains a lot of this. It also shows how much CO2 alone will stimulate growth.

CO2, light and growth of aquatic plants.
Thanks for the great article!
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post #8 of 13 (permalink) Old 10-22-2014, 02:29 AM
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Originally Posted by aggressor09 View Post
This is extremely helpful. Thank you.

For context, I have a 65 gallon now and am going to move the whole operation to a 75 gallon (same width but shorter and longer). I'm trying to determine what/how many lights to use, and what will be overkill before needing the addition of CO2.

One of my main concerns is that the plants aren't getting enough of what they need--my nitrate levels are very low and I've read (albeit sometimes contentious) information on optimum nitrate levels for plant growth. Is this something I should worry about, or just focus on algae growth or lack thereof? Again, just starting to assemble the pieces behind the science of aquatic plants...Thanks
For what it is worth, the light I had on my 90 was a two bulb T8. I ended up getting another like I said, but eventually settled on running 3 bulbs. This was mainly due to coverage issues...not intensity.
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post #9 of 13 (permalink) Old 10-22-2014, 03:01 AM
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I was under the impression that a 65g was built on the foot print of a 55g tank only taller ?
The Home Depot "Floorplate" light in T8/w two bulbs is a good level of light for the 75g tank. About $40. You may even need to raise it a bit
without CO2 in there unless you have several stemmed plants in the med/fast growing range.
I would suggest one each of GE "Daylight" 6500K bulb and one of the GE
"Plant & Aquarium" bulb in the white/green trim package that says on the package..."contains a combination of phosphors which produce light
rich in reds and blues".

The shortest distance between any two points is a straight line...in the opposite direction...
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post #10 of 13 (permalink) Old 10-22-2014, 03:26 AM
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It has been my experience that if you are wondering if you have to much light, you probably do.
I'd agree, but add that if you think you have enough light, you probably don't--at least not for the long haul.

I ran low light tanks for years before gradually moving my primary tank up to moderate light with a regular ferts schedule. Buying a bit more light than you really need gives you greater flexibility to move up and down the spectrum between the extremes and it's much easier to tone a too high light down than amp a too low light up. My other tanks all run at lower light levels, but I can still switch my various light bars around at will to suit--if the level is too high, I use a physical screen or a biological one in the form of floaters, or simply raise the light further off the tank.
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post #11 of 13 (permalink) Old 10-22-2014, 03:28 AM
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I'd agree, but add that if you think you have enough light, you probably don't--at least not for the long haul.
Touche
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post #12 of 13 (permalink) Old 10-22-2014, 04:08 AM Thread Starter
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Thanks for all the great suggestions. I neglected to mention that I'm using LEDs and plan to do so for the new tank, and also that both tanks have a standard width of 18 inches. I'm mostly housing shy African fish, which raises the conundrum of requiring a heavily planted tank with muted light.

I was initially shooting for an African biotope to build around my fish, so I ordered plants from far away and mediocre results (guessing shock from totally different water specs). I recently read an article suggesting that newcomers should just try a bunch of plants and see which type takes a liking to the water. I have some new plants booming, but they are far from African.

I'm happy to list my order/fatality/mediocre/progress list if it would help. Regardless, all of your responses have been very helpful--I very much appreciate all of the wisdom offered.

Thanks

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Originally Posted by Knotyoureality View Post
I'd agree, but add that if you think you have enough light, you probably don't--at least not for the long haul.

I ran low light tanks for years before gradually moving my primary tank up to moderate light with a regular ferts schedule. Buying a bit more light than you really need gives you greater flexibility to move up and down the spectrum between the extremes and it's much easier to tone a too high light down than amp a too low light up. My other tanks all run at lower light levels, but I can still switch my various light bars around at will to suit--if the level is too high, I use a physical screen or a biological one in the form of floaters, or simply raise the light further off the tank.
Great information--thanks very much. Would you mind sharing what floaters are in your tanks?
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post #13 of 13 (permalink) Old 10-22-2014, 06:20 AM
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I've used pretty much every floater out there over the years, but right now I've mostly got dwarf water lettuce, frogbit and a bit of duckweed after losing my entire floater collection last year.

Accidentally left a bin holding all my floaters behind on a trip to my new house with a load of plants and fish. By the time I got back, someone had stolen the bin and dumped all the plants out on the gravel. Saved a few pieces of frogbit and I found a good deal on the water lettuce here on TPT, but I haven't yet gotten around to rebuilding my collection.
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