How to stock fish that need to be in groups

Question
I've always understood that fish should be added to a new tank either 3 small fish or 1 medium/large fish at a time, to avoid huge ammonia and nitrite spikes. But I now understand that some fish should not be kept in groups smaller than 3, 4, 5, 6, etc.

So, is it best to introduce one, say Cherry Barb, then another the week after then another the week after, or add 3 or 4 at once and change the water every two days and hope they survive?

Thanks

60 litre tank (60x30x35cm)
Tank contains 5 zebra danios and 1 Siamese fighter
Internal filter (Tetra CrystalClear)
Tank set up for over a month, all levels as they should be.

Answer
Hi Tim;

Even though schooling fish should always be in groups it just isn't safe to do that in a new tank that is too small for more than one or two at a time. They won't like it, but it is best to still only add one at a time to establish a tank safely.

Your tank is actually at it's safe population limit, maybe even a little over so if you are considering more fish you probably should upgrade to a larger one. Your 60 liter tank can accommodate about 30 to 35 cm of fish. Your zebra danios will reach a size of about 6 cm each. Your Siamese fighter will be about the same because you don't have to measure those guys' long tails, just their bodies with an average tail length. This puts you at about 36 cm so I wouldn't add any more. Be sure to do normal maintenance weekly 25% water changes with a gravel vacuuming so it stays healthy for them.


At Your Service;
Chris Robbins