My new 20 gallon tank is cycled, and now I'm at the point where I need to keep the cycle going, either by adding ammonia daily or putting fish in. I already have 5 zebra danios in an existing tank, and am going to move them in first.

My question is about how many of the danios to add at once? Should I go one at a time, one every 3-4 days? Or should I add two this weekend, then the other three next week?

Would they be OK being separated in smaller groups?

I am sure some others will come in with some more detailed advice, but this is just how I do it.

I will admit that I have never had danios before, but with my tropicals I generally go by the size of the fish. If they are small fish I will add two to the tank every 4 days. If they are large fish I will add 1 per week. Keep an eye on your water levels though.

I don't like to add many at once so the water impact is gradual.