i got my hands on a bottle of superthrive and i was wondering if i can use this for flowering on a soil plant

You can use Superthrive all throughout the grow, but it doesn't contain any nutrients (N-P-K), it's entirely supplemental, so you'll still need to use standard nutrients along with it.

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and what does anyone suggest i use also cause i only realy have access to homedepot and i started getting i think they are nats lil flying bugs i wanna kill em what should i use