is CO2 necessary?

[Dangerdoll]

curious, I heard that a planted tank doesn't necessarily need CO2 injection with the correct lighting, is this true? If it is, wht would the lighting need to be (wattage) for sy a 55 or 75 gallon?

[TomFromStLouis]

Well, supplementing CO2 is not necessary. Diana Walstad wrote the reference on this subject, "Ecology of the Planted Aquarium".

But injecting CO2 allows you to grow some plants that need the extra help and light. Too much light without the other nutrients (CO2 plus ferts) becomes a problem. In other words, all plant nutrients, from light on down, need to be in balance.

So the second part of your question is the key: how much light is needed in a low tech tank? I think most would say that anything over 2-2.5 watts per gallon would call for injection. How much less would depend upon which plants you want to grow.

[plantbrain]

No, the tanks do need, but need is something you need to think about, you don't need chocolate, but you like it.

Plants, no matter what light level you give them, will do better with CO2 added.

At low light say 1.5w-2 w/gal, CO2 will really help the tank but the growth will not be so fast it causes a large problem.

For a 55 gal, 2x a 40w with a good reflector will do(say a cool white and Triton). Add CO2, either through a pair of DIY CO2 bottles or gas once you realize that CO2 is good and why the hell didn't you use it 10 years ago.

But if you cannot stand using CO2 but want to have decent plants, it can be done and requires a different approach, namely you need patience and set up the tank correctly from the start then leave it alone.

Most folks like CO2.
It makes up 40% of the plant's dry weight.

Fe, iron, only makes up 0.006% but you hear folks squawking all the time about adding that.
But CO2 is all no no no:)
A wee bit of Irony(pun intended)

Regards,
Tom Barr

[Cearbhaill]

It's all about balance- the right balance of light, plants, fish, and nutrients.
If you are able to luck into the right combination af all four you can have a nice tank full of beautiful plants with no CO2 supplementation.
If you get off track too badly in any direction you can have an algae farm.

I got very lucky and managed to get things right my first try.
I did this by adding a huge quantity of fast growing plants to eat up all the nutrients before the algae gets hold, plus supplementation with a variety of plant foods. I try lots of plant varieties, get more of those that work well, and don't mourn those that don't.
I can't grow java moss to save my life but my two red tiger lotus are growing like mad. Go figure.

[Dangerdoll]

thanks folks, that clears things up for me :D