DIY Co2 overload

i beleive you are supposed to check Ph for measuring the co2 content at before lights off. this will give you the highest Ph reading. any kind of surface splashing or bubbling will let the co2 out of the water

First of all, that's why they write recipes for DIY/CO2. Two things can occur when you add more of anything than the recommended amount. You can get a heavy burst of gas initially and endanger fauna.
And that burst can use up all of another ingredient that is necessary for the continuation of the reactor to produce gas and within a few days you get nothing, leading at times to a rise in pH which, you guessed it, stress the fauna.
Rather than remove the fish from the tank in case of a large pH drop, a large water change would equalize and re-set the tank for you. Then you can add an air stone to gas off excess gas until you can make up another bottle of yeast/sugar that will give you a more even flow/bubble rate.
When first beginning with CO2 of any type it is best to start it in the morning and monitor pH every 2 hrs. during the day. If you have greater than 20 - 25ppm/CO2 at lights out you will need to run an air stone over night or leave the lights on until your flow is adjusted downward, with in your case a more appropriate mix.
If you get a reading in the 20ppm range at lights out, the odds are that you will be safe over night. Then check the pH at lights on to verify.
Any time you see fish in distress.....gasping at the surface of listless and laying on the substrate an immediate water change can usually remedy the situation rather than moving fish around.

Len

the recipe i use:

1/4 tsp. yeast
2c. sugar
1tbsp. tomato paste (this provides food for the yeast, as it can't live very long on just sugar)

fill the container 3/4 of the way with warm water. let it sit open for a couple hours before attaching it to your CO2 reactor, as the yeast will use O2 at first before it really gets started, and it can't take a couple hours to start producing CO2