James, I moved your post to start a new thread rather than reviving and hijacking an old one.
Females will generally be larger, and will tend to be plumper around the mid-section. With having 5 of them you have about a 95% chance of having atleast one of each gender.
As for breeding danio and other egg scatterers:
I put 6 danio in a 10g with small red gravel substrate and had tank down to 50% water level. I left them there for a week, doing no waterchange in the time they were in there, but feeding lightly each day. I then moved them back to their original tank and filled tank to 100% water level, not removing any water that was already in there. I stopped feeding flake food for about 2 weeks. We instead put in 'green water'. Green water is water that has had a lettuce leaf decay in aquarium water to create microfauna, which is what the fry eat. Microfauna is microscopic animals. The leaf needs only be left in the water for 24 hours. Remove the leaf and pour water into tank. You can do that every day, but definately no less frequent than every other day. If it is a heavily planted (live plants) tank then it can be every other day. If it is not a heavily planted (live plants) tank then it has to be every day for healthy fry development.
The amount of water needed for green water mixture is only a half cup or 4 ounces.
That lettuce leaf in aquarium water needs to be put in direct sunlight. (Aquarium water is necessary because of the microscopic animals contained in the water. The microscopic animals are in all tanks. There is no way around having them in your tank water, other than having the tank be uninhabitable for fish.)
That sounds really complex, but it is VERY simple, especially after you've done it a time or two.
So summary:
Step 1: 50% water level in 10 gallon tank (40 liter)
Step 2: Leave 5-6 adult danio for 1 week, feeding lightly each day
Step 3: Remove adults back to their original tank
Step 4: Raise water level to 100%
Step 5: Daily 10% waterchanges recommended after adults are removed
Step 6: Put water from that aquarium into a bowl
Step 7: Put lettuce leaf in bowl
Step 8: Put bowl in direct sunlight
Step 9: Next day remove lettuce leaf and pour water in tank
Step 10: Prepare a lettuce leaf in aquarium water for next day's feeding
Hope that helped.
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