[Puffer Pita]

I dunno about comfortable but yes, I have backgrounds on all of my tanks because it seems to make them feel more secure. The skittish fish are less so, they are all more adventurous, calmer, etc. Their behavior/personality definitely changed when I added backgrounds, without exception. Doesn't have to be anything fancy either. I know people who are using garbage bags and brown paper sacks cut to fit. Anything works fine. I even used Christmas wrapping paper on some for awhile.