When the dwarf gets bigger you might have the eaten problem. A bigger concern of mine would be the toby fin nipping on the lion, puffers and related species are well know for this. Might I suggest a Antennatta or radiata lion instead of a dwarf. Both of these are perfect sized for your tank and tend to be much more open water swimmers than the dwarf lions, also much easier to feed and get switched to frozen food. Excellent choice of eel, very good temperment towards everyone else and not too big. Maybe a rabbitfish, dwarf angel or butterfly would be a good fish for you instead of the puffer, be better behaved and add some color, make sure you have good filtration if you chose to go the butterfly route.