CO2

[lmsmith]

I've decided I want a heavily planted tank. How do I know when to add CO2? What does it actually do to help, and what does a CO2 setup look like?

[suphew]

There are a couple of ways to do CO2, you can DIY with yeast, but IMO getting a bottle and regulator is the best option.

The reason you need CO2 is because just like terrestrial plants, they need CO2 to grow, and light and nutrients, you need to supply all 3 in balance, if you don't add in balance you will either end up with little extra plant grow or lots of algae. This is a possible reason why tank's in sunlight can get bad algae, i.e lots of light, but missing enough CO2 and maybe missing some nutrients.

3 things you need to CO2 setup, bottle (same as a CO2 fire extinguisher, but with tap instead of handle thing); regulator, this controls the amount of gas coming out of the bottle (you might also need a separate needle valve to slow the flow more depending on the regulator); and a diffuser, this mixes the CO2 with the tank water, there are lots of ways of defusing, I used to just feed my CO2 into my filter input and let the motor mix it. You might also want to get a bubble counter, this lets you see how much CO2 you are adding.

You can't really add too much CO2, the water movement in the tank will de-gas the CO2 releasing it.

[alanmin4304]

You don't need CO2. I have heavily planted tanks without CO2. If you want to do the CO2 thing you also need added fertizers and strong light as well. Any one without the others will not achieve much. With the right balance of all three you will get increased plant growth.

[suphew]

It also depends on what you want to grow, some plants particularly the redder one's don't grow well or at all with out strong light, fert, and CO2.

None of it needs to be expensive,

I used to use dalton's aquatic potting mix under a layer of gravel for substrate, this gives you all the fertiliser you'll need plus being in the substrate rather then in the water it doesn't cause algae, cost about $20 a bag which is enough for 2-3 4 foot tanks

Used 2 x 4foot batten light fittings and daylight tubes from electrical wholesaler, lights ~$30 and tubes less than $10 each.

Fire extinguisher converted, $10 for old bottle, ~$100 for conversion and certification, regulator ~$100.

[lmsmith]

Hmmm, that sounds hard and expensive.

Someone once told me that to grow their plants, they make up a bottle of sodastream, and pour it into the tank each day. Think it'll work?

[phoenix44]

never put soda stream in a tank!

ive done it as an experiment.

the pH will change drastically and so suddenly that it kills the fish.

i have photo evidence of the damage it can do as well (somewhere)...

make no mistake about it - CO2 changes the pH - forms carbonic acid.... lowers the pH far too much.

CO2(l) + H20(g) <-> H2CO3 (l) [in equilibrium]

[lmsmith]

Ok cool. Might stick with what I'm doing (turn lights on in morning, off at night, feed fish ).