Natural way to introduce co2?

A potting soil substrate slowly releases CO2 naturally... Walstad's book is a great way to learn about setting up planted tanks in a more natural way:
http://www.amazon.com/Ecology-Planted-Aquarium-Diana-Walstad/dp/0967377366

You can try using atmospheric pressure, that is what I use. In fact, that is how it works in nature. There is a constant supply of CO2 in the atmosphere, and when the tank water is lacking, then the atmospheric pressure forces more into tank. Just the opposite of outgasing. Water surface disturbance helps the process along. Then just scale you light and nutrients to match. Fish food has all the nutrients plants require, so I do not add ferts or carbon. Then I adjust my exposure time using timers.

i agree with qwe123, Miss Walstads book has been a great help.

Water can only hold so much dissolved CO2 under normal conditions, but there are actually quite a few plants that are perfectly fine under low light/CO2/nutrient settings. You wont see much growth however, but I always think live plants are a good idea. Definitely worth a shot.

jpappy789 said:

Water can only hold so much dissolved CO2 under normal conditions, but there are actually quite a few plants that are perfectly fine under low light/CO2/nutrient settings. You wont see much growth however, but I always think live plants are a good idea. Definitely worth a shot.

Click to expand...

jpappy is correct, there are quite a few plants that are fine using normal CO2 levels in the water. In fact all the plants on planet earth are fine using normal CO2 levels. What some people would consider "slow" growth is the plants natural growth rate under these conditions. When light/CO2/nutrients are available in overabundance, then plants will adapt their growth rate to suit the current conditions, and the growth rate can become so obscene that trimming is frequently required and suitable times to view your tanks "natural" look becomes infrequent. All that jazz about high output lighting, adding liquid fertilizers and injecting CO2 is just a different method for growing plants. And for some people it may be the best method, or only method. The truth is that it is the only method that drives the economic engine that supports this hobby. Buy more lights, buy more or better fertz, buy a fire extinguisher and point it nozzle into your fish tank. Good grief man when is it all going to end, somebody is going to gas all there fish after releasing the CO2 in under twenty minutes. Oh yeah, thats been done. Many times.

Plants are easy to grow. In fact they don't need our help at all. They have been growing on this planet without our help for a few billion years. Keep it simple, pay attention to them, talk to them if you think it will help, but most of all make sure they get plenty of water. In addition be sure that in your little glass box that you have just enough light to encourage the rate of growth you desire. Fish food has all the nutirents a plant needs, so don't feed your fish, feed the whole tank, fish plants and all. Be natural and let snails and worms grow in your tank, they can help manage your substrate which I recommend you use miracle grow organic choice potting mix capped with sand. Ask about it and I will go into the details.

a sump filled with some cave fish

Natural would be not adding any CO2 (which can work fine for plants so long as your light/nutrients are balanced). We increase CO2 to work around the natural state of things because you can make things look nicer than the natural state of things, and because nature can involve more algae than most people like. Balanced light, ferts, and CO2 helps grow healthy plants that outcompete algae.

But if you want a more natural *feeling* way, you could just exhale into the tank...
http://fins.actwin.com/aquatic-plants/month.9805/msg00446.html