Lol, yeah, I've had a couple of fish like that; have one now, in fact. You are making it even easier for yours to live a life of mystery, by giving him a cave with an elbow right at the mouth; he isn't visible unless he comes right to the end to feed. It helps him work on building his near-mythical status.
I have a Bristlenose Pleco now that I see maybe once per month. He lives in a fairly densely planted tank with lots of wood, stone, etc. and some fairly aggressive neighbours. If I really, really want to see him, I'll just comment to my wife that he must be dead and that I should search for a body. I think he senses this impending disruption to his world and seeks to build the legend a bit; he will suddenly appear casually perched in the open, remain for a few minutes, and then...poof! Gone, literally back into the woodwork...
Who knows what evil lurks in the hearts of men? The Shadow knows...
(If you "get" that reference...grab your cane, creakily lever yourself to your feet...don't trip on your walker...and pat yourself on your back, but try not to throw it out in the process.

)