I use 2 - 2L bottles and change one out every week, and put an additional tsp of yeast in the second one every week. If you have a HOB this will make it much more difficult to keep co2 levels up. You may end up changing both out every week, staggering them by a few days; or you could have three bottles, and change one every four days or so.

What is an HOB? Also, is it ok if this bottle is on the floor? Thanks again for the help! I just want to make sure my tank gets the best results possible. The good thing is everything is growing and nothing is really dying, but it does not look the greatest it can. That is the next step!

HOB = Hang on Back. This refers to any component such as a filter or wier (overflow box), UV, etc. Simply means it can be hung easily over the tank with no mounting issues......

You can keep your bottle in a bucket to keep it steady and contain any leaks....

Floor seems okay, but I have never done DIY c02, so no experience here..

Floor is fine. Just make sure you have a way of shutting it off when you take a bottle off, to prevent backsiphoning.

The Red Sea kit came with a venturi, that you can put it on a timer... which I have on a timer. I could make a 2L bottle so I will have 3 Liters all together... the question is how to tie the DIY to the red sea venturi so I have all 3 Liters going to the venturi. Another option would be to buy another venturi which I can attach the DIY to. What would you suggest?

I wouldn't suggest putting diy on a timer. Reason being that it can take a matter of hours to get enough co2 saturation into your water, if you turn it off overnight you won't have much chance getting it high enough by the next morning to avoid fluctuations when the lights are on. I'm not familiar with that system, but basically you need to tie the hoses together. You can get airline T's and valves that are made for using with airrator pumps, this is what I use to tie my bottles together into one line, then run that line into whatever diffuser/reactor you are using.

Any possibility you could send me a link to a place I can buy the airline T's and valves or link to a few images? If I could find them in a local hardware store that would be great so I would not have to pay shipping. Just wanted to get an image of what I am looking for. If I have 3 Liters going and I replace them every 1 to 2 weeks, would that be enough CO2 for the tank?

One of the members suggested lowering my lighting since it is 65 watts for 20 gallons. Can I buy a bulb that is 40 or 45 Watts. I am going to have my lights on only for 8 hours, so I think if I have enough CO2 and do the EI fert method, then hopefully I will be good. What do you think?