Beginner with 400w HPS- any help appriciated!

So i got a 400w HPS, and it is my first grow, i am trying to get the biggest wield so i am looking for any suggestions. I was thinking puting up to 20 plants in 2 gallon pots under my 400 would work very nice but i still question it. I am using some very good soil i bought from a grow store and i also have 2 different chemicals to mix with my water, not sure atm of the names, and i also have a bottle of "sugar daddy" for the flowering stage. like i said i am trying to get the biggest wield with what i have so any suggestions are appreciated!

I would put only 4-5plants max under a 400w u are wasting putting 20 plants, try pot of gold by flying dutchman seeds, hear they are large yelders

Mmm..yeah i agree with cyanosis,20 plants won't work under a 400w hps also buy an hps to mh conversion bulb for vegging personally i prefer 5 gallon buckets some strains have huge root systems you don't want to get a bad case of root-lock..