I just bought my girlfriend the same exact tank, a 2 gallon Eclipse Explorer. Do not follow the suggestion that comes with the tank. 10 guppies will not fit in a 2 gallon tank. Who ever came up with their suggestions didn't know anything about fishkeeping. I think a betta would be fine in the tank or a couple guppies. Danios are schooling fish and would require three or more and wouldn't look that good unless they were able to school. Thats why I suggested something brighter that doesn't need to school.