My friend has a just bought a three foot deep aquarium, he wants to keep six tiger barbs ,one rainbow shark and a couple of red claw crabs in there. He was wondering what other fish he could keep with them, who would not get bullied by the barbs or eaten by the crabs, he would prefer a range of smaller fish rather than a few biggish ones. Water peramiters about 24c and ph 7.4. Thanks all suggestions will be appreciated.