[jbherpin]

My suggestion would be Eastern newts, or, if frogs are the preferred, Mossy Frogs. Either way, I would add a bit to the water feature to make it less open and unnatural. I believe you said some plants have been added, but I would follow the suggestion of rocky areas, as well as adding some truly floating veg like duckweed or frogbit. If you are using a canister filter, be sure the outflow is not too strong.

All my best! BTW-I love the tank scheme and design, just not suited towards darts...

JBear