Neem Oil Question

well today when i finished filling my 25 gallon reservoir, i put all my nutes in... and i also put neem oil into the res. but i only put like 4 gallons worth of the neem oil. should i completely drain and refill my res because i put neem oil into it? or will it be fine because there isnt that much in the res?

NOOO. Change it, neem oil is meant for the leaves as a foliar spray, its going to stick to your roots and ruin your plants. And even when you do spray your plants with it i think it is only at like a 1tbs per gallon. Even if it is possible to use it at the roots it would have to be VERY diluted.