what is better for yeild?

So I just harvested and am not really happy with my yield. I used a 400w light for veg and flower, ff nutes no co2. My question is would i benefit more buy using a bigger light or using co2? My new clones are under the 400 and i cant decide what i should do . Please help with some ideas. Well off to work like a sucker.kiss-ass8 hours till happy time

Dude, 400w is plenty of light to produce awesome results......what kind of 400w are you using?

I use 400w HPS w/400w MH Conv bulb and it's fantastic.

400 W is plenty depending on the size of your grow area.... What was the heat like in your room ??? This can have an effect on yeild.. What type of plants were you growing ?? How many plants were you growing in the area ? Were you using soil ? Give me some more info and we may be able to give you a better answer, also try and send some pics... The is a wealth of knowledge on this web site, help us help you.

And remember you can always grow again.. Peace out )