No. Gravel poses an impaction risk in the gut because it is not digestible. Pet canaries have a much better diet than wild birds, and therefore they do not need to grind up the coarse seeds and nuts in the same way that wild birds do. However, it's fine to offer a soluble source of grit, such as cuttlefish or ground-up oyster shell, if you feel happier giving your birds something to help mash up seeds in the gizzard.