You don't have to keep ordinary fish if you want to be comfortable at the end of the day and get your cut of calmness as you can also keep hermit crabs, which are also very challenging and fun.
In fact, more and more people have started keeping hermit crabs in their bedrooms and there haven't been any complaints so far, at least fro what we know.
It might be a bit difficult for you to make up your mind about the kind of such crabs you want to keep since there are so many species, but, as you can imagine, each species is different, has different demands and different personalities.
There are a lot of such crabs which don't like the idea of adaptation very much, but there is a way to handle this kind of crabs, too.
You can go for a red hermit crab for instance or for a white spotted hermit crab, a very beautiful species with red legs and black spots on them.
However, this species and coral reefs don't make such a good pair, but you should remember that the white spotted hermit crab is very useful with algae.
Also, you should pay attention to the environment you provide for the crabs because they are not exactly the most sociable creatures you have ever seen.
One fascinating thing about these crabs is that they have new shells for when they grow out of their initial ones, but there are also many more such curiosities.
Therefore, if you want to be more special, you could also try keeping hermit crabs because there are very high chances that you will become just as fond of them as you would with fish.