You don't plan to keep them together do you? If so I would strongly recommend not to do so because it will not end well for one of them. But if not pacs that small you could split 10 gallon into 2 with a divider so they cant see each other. Or maybe a 20 high split in 2 but I wouldn't go any bigger then that for pacs that small, out of all honesty I would split a 10 for now.