Saltwater aquarium crabs can be very entertaining pets, as well as great scavengers that can help to clean out uneaten food from your aquarium. Crabs will feed off of dead and dying organic matter, such as leftover food and dying plants in the aquarium. Some people just like to keep crabs in the aquarium...
Gobies
Tom aquatic mini deco 1 gallon all in one build
Tom aquatic mini deco 1 gallon all in one build day 4 - Aquascaping