Yes an admission I'm not talking about mixing Darts or Mantellas but a small group of tree-frogs with a small group of newts and a few small lizards worked well for me for over two years and I still keep the newts and lizards together even now, it adds interest to a large viv providing they don't compete for food and don't bully go for it. For example my newts ate maggots but wouldn't touch flies they turned into but my tree-frogs loved them.