A small industrial ultrasonic cleaning tank, which is one of the best-selling models, had cleaning problems. Customers sometimes complained that the tank did not completely clean all objects, or that some objects got damaged, so a solution to the problem was urgently needed. The tank has a volume of 18 L, frequency of 28 kHz, eight horn style PZT4 transducers, and a total electric power of 400 W. The cleaning occurs from the cavitation effect which corresponds to an increase in the acoustic pressure. A computer simulation is presented using a harmonic response analysis (HRA) in ANSYS to resolve and improve the efficacy of the tank. From the simulation, we found that the acoustic pressure within the tank was uneven. The distribution of acoustic pressure had a characteristic pattern depending on the placement of the transducers. When the temperature was increased, the acoustic pressure was decreased leading to a cleaning efficacy drop as well. All simulation results were correlated to the foil corrosion test and power concentration experiment. The HRA was used to redesign the tank for higher cleaning efficacy. The simulation results indicated that more suitable placement of the transducers lead to a more intensified acoustic pressure, and a better distribution throughout the tank. This research not only resolved the cleaning problems that occurred in the 28 kHz tank, but was also demonstrated that it can be applied to a 40 kHz tank as well. Results from this research were accepted and approved by the manufacturer, and were used by them to develop smarter industrial ultrasonic tanks with higher cleaning efficacy for commercial sale.