My first senegal is in a gravel tank, but it's fairly large gravel. My two recent acquisitions are in my first sand bottom tank in over 40 years of fish keeping. I like how it looks and it is apparently safer for them. But am I going to change the gravel bottomed tank? Probably not.
Yeah I have gravel in my tank as well and I don't think it has ever been an issue. I have seen them put gravel in their mouths thinking it was a hikari pellet, but they eventually spit it out. I have somewhat large gravel so it's not as much of an issue as if I had fine gravel. Sand is a better substrate to keep bichirs on but it's harder and more time consuming to clean. I do my gravel vacuums with my water changes and call it a day. Just a matter of personal taste.
i have gravel in my tank and when i feed my sen sinking pellets a lot of times he nabs a piece of gravel by mistake, but he always spits it out.. he'll be fine in a gravel tank, once its in their mouth they're pretty good at distinguishing whats food and whats not..
i'm keeping my bichirs since 14 years with gravel and lost in this time only two individuals - a senegalus by constant overfeeding and a endlicheri by bacteriosis two days after buying him.
An important point may be the size of the gravel and the geometry of the surface of those single particles. Aware from this black vulcanic gravel of glass-like consistence and razor-sharp edges when keeping any vertebrate bigger than 4cm! This will not only cause interiour injuries, also injuries of the slime-coat ( that will open the door to the super-deadly bacteriosis!) !!!
My bichirs have "learned" to spit out everything that is no food - even with pellets of similar size ...