Black light??

My plants are in flowering stage...

i have been told that blacklights can be effective in this stage..

Is this true?

no, not at all. stop taking advise from whoever gave you that golden nugget of info.

na keep useing a normal light but switch it to 12/12

Whoever told you that is confused. What they were probably referring to is UVB light (blacklights are UVA). Reptile lighting is what you need for UVB, but do some research on it's use first, then decide if you want to bother. It's not essential, but it can increase trich production.