Originally Posted by Dovie
I can see your point, the C02 set up was not expensive and I hope it will help get the plants established.
Concerning the wheel breaking the surface, I was under the impression that the surface needs to be broken to help oxygenate the water. The air stones that people put in the tank does the same.
Aerate the water perhaps. I would expect that without dripping O2 into the tank it won't oxygenate so much as off gas the CO2.
When we test tap water right from the tap the abundance of CO2 in the water skews the pH readings. Shaking the water in a bottle for a minute off gasses the CO2 to the normal capacity for the water and the pH will be more accurate. While shaking a bottle is obviously more vigorous than a bubbler, it does the same thing. The plants serve to produce O2 which is in the water for the fish to use.
The best source of nutrients for the plants becomes the ammonia (nitrogen source) and CO2 (carbon source) that the fish produce and either trace minerals in the water or in a fertilizer that we add. Alternatively the carbonic hardness in the water is another source of carbon (Calcium Carbonate). Of course adding other supplementation might be necessary in order for the total balance to allow the plants to take up the ammonia and CO2.
Only after the total supplement balance is established along with the light required to allow the plants to photosynthesize everything and CO2 is found lacking should it need to be added. In some high energy systems the nutrients and light are overdriven intentionally and more carbon is needed to allow the plants to use everything that is thrown at them. Perhaps CO2 is the easiest to add at this point, I might think that increasing the KH to compensate for it's reduction may be as effective.
In my first tank setup I had one fish for a period. Plants thrived. KH lowered as much as 25% after water changes as plants used what they could from it. Added lots of fish, KH is now stable, plants are growing about the same... fast. I have a small plant only test tank on the go. KH has gone down over 50%. I'll be adding water to bring it back up this weekend and adding a few more plants even though it is already heavily planted.
Plants will take carbon from where they can and I'm not certain that CO2 is the easiest source to provide this even if it might be the easiest for the plants to utilize.