The below paper suggests that with approx 2.4mWsec/cm2 it's possible to inactivate 99% of viruses. No specific mention of coronavirus, but could we use 13W aquarium UV lamps (are they UVC?) for an effective solution?
https://www.researchgate.net/profile/Chun_Chieh_Tseng/publication/239392662_Inactivation_of_Virus-Containing_Aerosols_by_Ultraviolet_Germicidal_Irradiation/links/54f823b80cf2ccffe9dce501/Inactivation-of-Virus-Containing-Aerosols-by-Ultraviolet-Germicidal-Irradiation.pdf