That's only because the shark wasn't cared for properly. I've kept hundreds of bamboos on 'gravel' without issue.
Again, the link says 'catshark', but it's a bamboo. Catsharks have a different jaw structure. I HATE Live Aquaria. They have so much wrong info that they shouldn't be allowed to sell fish. And just for information's sake, they only look like that when young. As an adult, they have very faint banding, and look almost a solid tan color. Also requires WAY more than the 180 gallons they suggest. That will be over 3 feet long when fully grown and need space to swim freely. I also wouldn't consider them an 'aggressive' shark at all. In fact they are widely used in public aquarium touch pools.