I mentioned tree frogs because your tank is vertical. Many of the beginner dart frogs would prefer a horizontal tank. You could do it but I think it would be benifical to landscape properly to help the frogs use more of the vertical space.you would also need to get panes of glass cut to cover up the screen lid to keep in moisture. You would need to learn how to culture your own fruit flies. Although that seems like a big hurdle it is actually one of the easiest parts of keeping darts. There are some beginner darts that I would reccomend that you check out. Dendrobates Leucomelas, Dendrobate Azureus, Dendrobates Tinctorius just to name some popular ones. These frogs are diurnal unlike the nocturnal tree frogs and they are bold so they will be moving around more than the tree frogs. BUT they are less forgiving to beginner boo boos.They need very specific environmental requirements and the owner must be certain he can maintain them consistently. Only you know if you are a diligent pet owner. If you have a dog out back that you rarely visit or fish that you haven't fed in a week than darts would not be good for you. Or really you would not be good for the darts. They are the most active as far as frogs go but they do require a higher level of responsibility. If you think your up to it check out those species that I mentioned and if your still interested then we can go into details.