Cultivating drug-type Cannabis sativa L. with aquaponics could reduce mineral fertilizer use; however, its nutrient solution is often unbalanced and low in K⁺ and micronutrients. It is unknown if a K⁺ fertilizer, a micronutrient fertilizer, or both, would improve C. sativa production in aquaponic solution, as optimal K⁺ and micronutrient concentrations in the root zone for C. sativa during the flowering stage have not been investigated. To determine the effects of adding a K⁺ fertilizer and a micronutrient fertilizer to aquaponic solution for C. sativa production, we grew drug-type C. sativa in five aquaponic based solutions: aquaponic solution (control plants) (15 mg·L⁻¹ K⁺); aquaponic solution with added micronutrients (Fe³⁺, Cu²⁺, Mn²⁺, B³⁺, Mo³⁺, and Zn²⁺); and aquaponic solution with added micronutrients and three K⁺ concentrations (75, 113, and 150 mg·L⁻¹) during the flowering stage. To evaluate the impact of additional K⁺ and micronutrients on C. sativa production, we measured growth (vegetative parameters and weight), physiology (leaf gas exchange), leaf nutrition content, and yield (inflorescence weight). Adding the K⁺ fertilizer at 75 and 113 mg·L⁻¹ with micronutrients to aquaponic solution increased harvest index (marketable inflorescence to shoot weight) by 16% and 22% compared with the control, respectively. Cannabis sativa dry apical inflorescence and total inflorescence yield also increased linearly with increasing K⁺ concentration. Alternatively, plants grown in the control (suboptimal K⁺ and micronutrient conditions) had no difference in growth or measured physiological parameters compared with plants with supplemented nutrients. Our study suggests that aquaponic solution mitigates low K⁺ concentrations from causing deficiency.