Reply To: Tank size & a few Q’s
Welcome to the forum! 
How many can I keep in a 4 gal cube, 10 X 10 X10?
3 would probably be best, maybe four.
Can I keep more than 1 male, all males?
I find one male and two females a good combination. Plus if you ever feel bad about this species going extinct in the wild, and their natural habitat being ruined, you’ll potentially be able to breed them…Males are the prettiest, but don’t get along with each as well as males and females, or females together.
Anyway, males get all colorful for females, but one is the “alpha” so others will not be as colorful.
I was thinking 3 or 5?
Again, 3, but that’s just me.
Are they known to jump?
Yes! I’ve lost two this way, as have others. 
What ph do they need?
Between 6.2 and 7.8 is good.
Are they like other danios, always on the move?
Quite sedetary actually, unless frightened.
What do they eat, and how often should they be fed?
Normal food is alright. They do better on quality foods, like Hikari mico-pellets, and small live foods. As for food, a little bit twice a day is best, or more in one feeding if convenience is an issue.
Hope this helps. 
What fish have you had before or keep at this time, by the way? And these fish are all you plan to have in the tank?
– Atlantis