Is CO2 really necessary?

  • #1
I’m going to try my hand at a medium to heavily planted tank. Is CO2 really necessary or do I just have to have the right amount of light? O its for a 29 gallon.
  • #2
I'd try the right amount of light. We had a CO2 canister set up & lots of light, in our old 100 gallon tall...the algae got overwhelming to the point most of the plants died. It was a green slimy mess in there.
  • #3
they sell a product called fourish excel, which gives the plants co2, but ina liquid form of carbon. works great!

lighting is more important then co2, because its naturally found in the tank
  • #4
I think it mostly depends on your lighting levels -- what kind of bulbs and how many are you going to be using? Higher light levels promote faster plant growth, then the plants need more nutrients to make that healthy growth. As a result you have to be really careful to provide enough carbon, iron, etc. for your plants. In a lower light situation, you have a lot more leeway (though your plant choices are limited).
  • #5
It really depends on what plants you want to grow. Then figure out what lighting you need to grow them If I'm not mistaken over a certain amount of watts of light you need CO2.
  • Thread Starter
  • #6
DO you know what that watts is that ill need CO2 after that point?
  • #7
DO you know what that watts is that ill need CO2 after that point?
No but I will try and find out
  • #8
A lot of resources I've seen say that once you have over 2-3 WPG of light, then you should be looking into a CO2 system. So if you have 60 or more watts of lighting on your tank, then you should be considering a CO2 system.

Take a look at this:
  • #9
Thanks for the link nugzboltz, I enjoyed the information and am still hoping to expand into more plants in my tanks, this helps.
  • Thread Starter
  • #10
thank you it was very informative
  • #11
This is the answer I got when I asked that question

  • #12
Planted tanks!! Wheee!!!!

C02 is sweet but not 100% needed. The lower light = lower maintenance approach is best for most people. When you get into high light and C02 set ups you need to devote more time to the tank. Check out for tons of information ont he different ways you can do planted tanks.

I have an over light issue that I am currently sorting out, and I am using DIY C02 as well as excel... Whew.... Lot of initial work here but it'll get figured out..
  • #13
What Gargoyle said on the lower light = less maintenance is the approach I've taken.

I look for plants that need moderate-low to moderate-high amounts of light and run with them. I just can't afford a CO2 setup right now. The more light a plant uses, the more CO2 it needs, which means that the high-light plants need a lot of CO2, so I just avoid those.
  • Thread Starter
  • #14
so a 30-35 watt bulb would be only ok for low light plants, or can I get moderate to low?
  • #15
Plantgeek has Medium Low light plants listed. Watersprite worked for me at 1.25 W/gal. Guess it depends.
  • #16
That's pretty much low light but you can grow lots of things in low light.
  • #17
so a 30-35 watt bulb would be only ok for low light plants, or can I get moderate to low?

Depends... If it is a T5 HO set up you would be considered high light because of the actual penetration of light that a T5 HO bulb can achieve. I just found that out the hard way... LOL!! Plus the Lumen output is considerably higher than what you would think.
  • Thread Starter
  • #18
for right now its just a better bulb for the hood light that comes with the tank. but there are enough low light plants to give me a good variety
  • #19
I just added some low-light live plants to my tank for the first time today. After I put them in I started wondering if it is necessary to add co2. I added Java Fern, Anubias, and Crypotocoryne. I would like to avoid the added expense of the co2 if it isn't needed. If it matters the plants are all 3-6" tall. Total of seven plants (although some are bundeled and count as one).
  • #20
CO2 is not necessary until you start providing higher levels of light. Exactly where that threshold lies is debatable, but it's certainly higher than the .72WPG your aquarium info indicates.
  • #21
Excuse my ignorance, but what does ".72WPG" mean?
  • #22
Ah, It just clicked- "Watts per Gallon"
  • #23
how do you find out your hoods watts
  • #24
how do you find out your hoods watts
Read the watts indicated on the bulb, if you have more than one bulb...add them. Hope this help.

GMCMaxx, you might need more light. I had <1WPG and my plants were not doing that great. I now have ~1.4WPG and the plants are looking much better. Just keep an eye on the plants for a few weeks and if they don't look good, the first thing I would look at is increasing the light.
  • #25
GMCMaxx, you might need more light. I had <1WPG and my plants were not doing that great. I now have ~1.4WPG and the plants are looking much better. Just keep an eye on the plants for a few weeks and if they don't look good, the first thing I would look at is increasing the light.

Thanks. I'll keep an eye on them. I've increased the amount of time my lights are on by a few hours to help the plants more. The plants have been in the tank for about a week now and I can see some new root growth on the anubias.
  • #26
I agree with the above statements....light is the most important. My tank is maintained with a 32Watt bulb (4ft standard aquarium light). All plants are doing good except micro swords which are too far from the light. I do approx 10 hours per day...and mostly low light plants except near the top.
Here is a pic of what works for me. IMO CO2 is not necessary.
I should up the wattage some day....those regular sword plants are 3 years old!!!


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  • #27
if you are worry about the CO2 insufficent you can try to add in more fish as the fish will provide more CO2 to the tank.
  • #28
That's a good looking tank there Ted.

Speedo, what's your theory behind more fish means more co2? I've never heard that one before. I would really have my doubts that if the fish produce co2 it would be in sufficient quantites to make a difference to plants.

GMCMaxx, I don't think co2 is needed in a low light set up either. If you do add more light it may be needed but I don't think anything under 1.8wpg really gets much benefit from it. If you want to experiment with co2 a little try doing a diy co2 set up. That way you can see if there are any benefits to be had in your set up without incurring any great expense.
  • #29
For what I know as long as it wasn't overstock and the plant isn't that much, the CO2 produce by the fishes is sufficient for your plant to do their photosynthesis.

But if you have a very heavy planted aquarium, you would not like to try this as the fishes could not produce that much of CO2 which is sufficient to supply to the plants you had in your aquarium.

Photosynthesis is the process, whereby plant make food with water, CO2, sunlight, and nutrients from fishes poop or some other food watse.

Therefore, if i'm right and following the process, the plant actully can take in the CO2 produce by the fishes. Again however, if you had a really heavy planted tank, better buy a CO2 tank. For GMCMaxx case, I think there's no need of the CO2 tank.
  • #30
I'm very aware of the processes Speedo, I was wondering how the fish produce co2 & why you think it would be enough to assist plant growth. I've read heaps aobut planted tanks & been keeping them for many years as well as knowing lots of others with planted tanks & this is the first time I've ever heard anyone reccomend adding more fish to produce co2. I think the co2 your talking about is actually the 3-4ppm that is present in our atmosphere & mixes into the water during oxygenation. I'd like to see some evidence to the contrary though.
  • #31
mmm, because my LFS said that I had enough fish to support and advise me not to buy the CO2 tank first. and this is what he had explained to me.

and fish do breathe right, and they take in oxygen and breathe out carbon dioxide. that's is why i'm saying fishes produce CO2.
aquatic mouse
  • #32
I never used a CO2 machine in my planted tank. I did use a plant fertilizer called Flourish. I swear by this stuff. It WORKS! My wisteria was growing like crazy. I kept having to bring clips to my LFS to keep it from over taking my tank.
  • #33
Sounds like you just didn't need co2 to be added Speedo. The amount of co2 produced by fish, even in an overstocked tank isn't even going to raise co2 levels by 1ppm. Certainly not enough to make any difference to your plants. The only benefical thing the fish do for plants is produce ammonia which the plants take in as a source of nitrogen. The amount of oxygen actually taken in by a fish is absolutley miniscule & even less of that is expelled as co2. I'm afraid I just can't see it making any noticeable difference. Each to their own though & at least your LFS didn't try to sell you something you seem not to need. I'm also interested in Aquarium two in your Aquarium info, that bit about 5000w lighting is a typo, isn't it?

Aquatic Mouse, Flourish is good stuff all right. I've been using it for many years in my tanks always with good results. If you have enough lighting to make use of it, try out a diy co2 rig sometime. Your plants might go ballistic then. Doesn't sound like you need it though. No point messing with something that already works well unless your in the mood for experimenting.
  • #34
sorry for the misunderstanding nutter, I understand what you mean. as I always thought that the fishes produce the CO2 would be enough for the plant. thanks for telling me that the fishes even overstock wouldn't even incressed 1ppm thanks.
Janine arm
  • #35
I'm thinking about doing plants in my aquarium, but I really don't want to mess with co2.
  • #36
This greatly depends on the plants you have. With the right plants there's no need for co2 to have healthy growth.

  • #37
Nope, not necessary at all! Just be sure to pick plants that don't need it. A few do for best success but most will get plenty from the livestock in the tank
  • #38
  • #39
God I'm jealous of that tank! Is that jungle val? DoubleDutch

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