I have housed a few of these over the years, I have a small one now. I think the food they consume other than wood when the lights go out (and there is left over food) is a variable. I noticed that when I moved one from a 90g to a 180g that it grew an inch in 6 months or so. This was years ago ...

It is striking regardless of what brought it to this state. Perhaps an ichthyologist somewhere could explain it.