Believe it or not the Flex seal tape works pretty well. I watched a video done by a news station with one of their consumer product experts and they tested Flex seal tape and it performed just like shown in the commercials with the water leaking from various repairs.
If you do wind up using Flex seal tape it is only meant to be used until yuo can make a proper repair. Since it is at the corner of the tank and resting on the angle bar I'd probably add a piece of pipe insulation wrapped around the corner to help keep any vibration from rubbing through the Flex seal tape.