Hi there, thank you, I appreciate that
Unfortunately I think the gravel may have been an issue, it was in fact on both the dry and wet sides of the tank, situated at a sloped angle. I went to the pet store yesterday and bought some cypress mulch bedding and a wet dish instead of the setup I currently have, and I fed Bogart in a separate feeding tank today to make sure he would't ingest any gravel accidentally. I do think that may also be true about Hercules though, he did not seem the liveliest when I got him, but I wanted to help.
Thanks for your reply LordofStuff12

Chrissy