you can possibly put some Neon Tetra's. I just read the following.
"Neon tetras are considered easy to keep in a community aquarium of at least 10 gallons, with a pH of 5.0–7.0 and KH of 1.0–2.0. However, they will not tolerate dramatic changes to their environment. It is said by some that Neon tetras should be kept with at least six other (preferably ten others) of their kind, as they are considered "school fish. They tend to be timid and, because of their small size, should not be kept with large or aggressive fish who may bully or simply eat them. Fish that mix well in an aquarium are other types of tetras, such as the rummy-nose tetra, cardinal tetra, and glowlight tetra, and other community fish that live well in an ideal Tetra water condition. Mid-level feeders, they are best kept in schools of five to eight or more, for the "shoaling" effect when they move around the tank. They shoal naturally in the wild and are thus happier, more brightly colored, and more active when kept as a shoal as opposed to singly. Their colour and the iridescent stripe may become dim at night, and can be virtually invisible after a period of darkness. The color may also fade during a period of stress, such as human intervention into the tank. Neons are best kept in a densely planted tank with subdued light and an ideal temperature of 20–24°C (68–74°F) to resemble their native Amazon environment."