I have 2 zebra danios. They are very active but fun to watch. They play all day long with my neon tetras. My female was just pregnant and laid its eggs but I can't find them. My parents think that the other fish ate them. The other fish I have are a Gourami, pleco, 2 neons, and 2 saddleback cat fish (cories). When the zebras were courting each other the male would chase the female all over the place. The female became very very round.
I just got 6 of these guys a while ago. Added them to a ten gallon well planted tank that already included 2 Cory cats, 2 neon tetras and 1 otocilincus. At first it seemed the neons were a bit nervous. After a day they all started shoaling together. The neons even picked up the wild danio, like tail wag.
Two years ago I bought 4. I still have to 2 and they are very peaceful towards my other fish. The only problem I have with them is that they jump out of my tank (that's how I lost the other 2) and I can never find them.
Zebra Danios add great movement to a slow moving tank. I currently have 2 zebras in a 75 liter with 4 dwarf gouramis. The danios make the tank easier to look at, and they keep you entertained sweeping throughout the plants and the rocks and the water, one gets lost quite often because he's missing an eye... poor bugger.
Zebra Danios are fascinating! They give a cheerful mood to the whole aquarium as they begin swimming together in schools or chasing each other joyfully. When I change something in my aquarium or get too close to it, they begin swimming in schools. It seems to be a defensive response to my "intrusion". Otherwise when everything looks OK for them, they tend to be more territorial - the stronger ones claim some region of the waterspace and will chase any intruder, specially if these are other zebra danios! Their reproduction is very easy as Meryll Green pointed out. I bred zebra danios once, about 100 grew. Nowadays, about 35 of them live with some more adult zebra danios in a community aquarium. They won´t be succesfully bred when other adults are present because they just love to eat their own eggs. In their larval stage they are still too vulnerable because they stick to the glass, rocks, filter and can be easily spotted. They begin free swimming only after their own egg yolk is fully consumed, 1 to 2 weeks after spawning.
The zebra danio is an excellent fish. The reason many people have problems is because you should have at least 5-6 danios together. This takes a big tank though. They breed often in the community tank, but then turn around for a caviar snack. I have one male with 5 females and sometimes I see them chasing around the tank. If I have a spare tank I move them to that and half of the times they lay eggs. They need at least 4 liters to gain speed on the runs across the tank. The small larvae are about the size of splinters and are black when viewed from above or below. They dangle like ornaments from the gravel glass and anything else they happen to stick on. Zebra danios should be kept in schools where the dominant fish chases the others around. Active and playful, my school often twists at lightning speed through beds of hornwort or they chase each other around Vals. Despite the fact that it is susceptible to mouth fungus this fish is a must for almost any tank.