@Lacy It most likely will be the only one kept in this aquarium. The tank is only 50 gallons and Ellerkeldia rubra is semi-aggressive/territorial. Within a few hours it claimed the main rock structure in the aquarium. The fish is very interesting fish to watch. There is limited information available on this fish.
From Jake Adams at Reef Builders
"Ellerkeldia rubra is an exciting new dwarf seaperch species that is very rarely collected from Western Australia. The Ellerkeldia genus includes many species that greatly resemble Hypoplectrodes sseaperches but Ellerkeldia has a slightly more elongated body shape. Although a few specimens trickled into the U.S. last year from the west side of Oz, this recently imported specimen from Russo’s Reef is the first specimen seen in over 12 months. Based on the color pattern and behavior it is believed that the red-striped dwarf seaperch might be seen at moderate depth but like Hypoplectrodes and Plectranthias they may become more abundant with increasing depth. E. rubra has been recorded to reach almost 4″/10cm in size and with a capacious mouth making up a significant part of that length, we wouldn’t trust this little predator with small fish or crustaceans adn you can kiss your cleaner shrimp goodbye!"
Mike