I have six danios, three pearl and three leapord (two long finned, so pretty!). All in my 25 gal tall tank. They are sooo active, just what my tank needed when i got them. They aren't really schooling fish but they tend to stay together at the surface most of the time.... and follow each other around just to play. I did notice that one of my long-finned leapords got a nip out of his tail fin, and i think one of the other danios did it. They leave all my other fish alone, maybe because they are the smallest i dont know.
Your tank looks good, lots of room for the danios to swim. But they do like to play in the busy plants sometimes.
I think any substrate that is fairly large, (even just on surface) is adequate for the fry to hide in. I got my gravel from the river near my house. Its got small rocks like the gravel you buy in pet stores on the bottom, then larger rocks up to about an inch round covering the top inch or so of the substrate. I extensivley scrubbed and boiled the gravel before it went in my tank, and it was well worth it. Just having that kind of gravel makes it look so natural! anyways, my krib fry hide easily in the rocks. I can never find them until thier mom wakes them up in the morning.
