I think that if they do that, it's to either find food or to possibly escape undesirable water conditions in search of better ones. Either way...your captive ropefish should not have these concerns. If they are well fed and well maintained, I would bet that they will never use such facilities.
Fish...even lung-breathers like ropefish or walking cats...are unlikely to go for a stroll just for a breath of fresh air.
Build something and try it...keep us posted, please!
That looks like a healthy fish. How big is it?