Look into the rapid Rise...it takes less than 30 mins.
If you are not running 2 DIY systems you are going to be running into BBA soon. BBA occurs when there is a lack in co2 consistancy, I know it's hard to reach 30ppm with DIY but in my 55 I was able to achieve this with 3 units.
I am currently running two. I thought I would get enough with two and my higher fish load, but that doesn't seem to be the case.