Lighting help

[Deontae]

Hey guys I am upgrading from a 20long to a 40b and need new lights. I’m thinking of getting the viperspectra they make a 16inch version and a 31inch version. My question is should I get two of the 16 or will the one 31 be fine?
Thanks

 

[xxkenny90xx]

Either will work fine but I like having just one fixture so 31 would be perfect imo

 

[Deontae]

Do you think just one of the 165w would work?