Jack Wattley discus, in advance of Hurricane Irma in 2017:

To all our friends and family in the fish world facing this incoming catastrophic event we ask that you stop feeding as of today and start doing 10-20% water changes every day until the day you cannot. This will eliminate a lot of the ammonia which will kill your discus once the electric fails. If you do not have a generator use hydrogen peroxide. Mix one third cup in a solo cup with tank water and distribute it evenly. I kept my tank at home alive this way for two weeks 12 years ago. I killed all the plants but the fish all survived.