maybe, maybe not
Too high or not too high will depend on the CO2 that is in your fish tank. You can measure this by using a CO2 test kit or testing KH and pH and using a chart to determine the CO2 level indicated. Generally, 20 to 30 ppm of CO2 is all you want, if the fish are not accustomed to the CO2 then they may be uncomfortable with even a lower level initially.
Now, the CO2 IN the tank is affected by the CO2 ADDED to the tank, the bubble rate, as well as the CO2 absorbtion rate which depends on how you are mixing it in the water, and it depends on how much CO2 is lost to the atmosphere which depends on the surface agitation of the tank and how well any lid may fit. It also is affected by the other sources of CO2 in the tank, the bacteria and fish, and the CO2 usage in the tank, the plants.
If this is a DIY set up, you can reduce the yeast added next time, if the CO2 measured in the tank is indeed too high.