15-30-15

Hello again, Ok i got some fert's from a friend and it says for flowering, veget.. and Ect. But the shity part is that he lost the bag or box that it cme in, so he said he THIKNS'(wich really aint good for me)that is should be 1 "heaping" spoon full per gallon. So can anyone tell me if this is right, and if 15-30-15 will even work for me. or should i look for something els, all i could find ot here so far is 10-10-10, and i didnt get it cause i got this 15-30-15 for a friend. But someone did say that 20-20-20 is best.

If what i have is ok, then will u tell me how "often" i should give it to my plant and "how".?

What do u guys think