I was thinking of making my own CO2 system for my 55G out of some larger Washed plastic bottles. I was thinking this. Please let me know if Im doing something wrong since Iv never used CO2.

I was thinking of taking two bottles, getting them connected and filled with the CO2 mixture. I was going to use a Maxi Jet 400 for the disffuser. I would get the bottles connected to the disffuser and all that.....

Here's the Question: Which one sounds better and won't cause a crash
1. Turn on a bubbler a hour before lights go out and turn it off a hour before lights come on. With the CO2 running into the tank all night.

2. Have the CO2 start a hour before the lights come on and turn it off a hour after lights go out.

I have eco complete as the subtrate and I hear its better to let the plants eat the fish waste. And under filtering you tanks better then over cycling. But of course I would still do the weekly water change. I was thinking of using 2 maybe 3 sponge filters and thats all.

Also what are some good types of CO2 test's? Also how would I control how much CO2 goes into the tank? And what should the CO2 level be?

Use #1 with the following changes: Have the bubbler go one right when the lights go out. CO2 outgasses very quickly.

2 or 3 sponge filters for your 55 gallon? How are you going to stock it? It's not going to be enough. I'd go with a canister filter.

CO2 tests? Drop checker. Search the DIY forums. There's information about the recommended levels of CO2 in that thread. With DIY CO2, you'll always (pretty much) be supplying less CO2 than the recommended levels, so controlling the levels of CO2 going into the tank won't be too big of an issue.

Turning off the flow from DIY CO2 mixture can lead to a huge mess if the bottles rupture. With DIY CO2 you have no actual control over the amount of CO2 that enters the tank. You can control how many bottles of mixture you use and with a more complicated setup you can keep an even temperature of the mix. But how much CO2 is generated is up to the yeast.

Sponge filters make great biological filtration but don't provide much water movement. Not to mention the space they take up in the tank.

Get a canister filter. You will be much happier with it. The plants don't "eat" fish waste. They eat the breakdown products. And no matter where the fish waste goes those products will be in the water.

I thought number one sounded best as well. I was also thinking that turning off the Diffuser would cause troubles but did not know so asked.