How important is group size?

[Riverfishcommunity]

Just a question I've been grappling with.

I have rummy nose, cardinal and neon tetras. When purchased I got the minimum group size i.e 6

As I've gotten more experienced and gone on to bigger aquariums and bigger fish and with the passage of time the numbers of my 'first' fish have dwindled. Leaving me with what I now have - 3 rummy noses. 4 cardinals. 3 neons.

These tetras are now in an almost 300 litre tank and seem happy enough bumbling around. They are in with peaceful community fish.

But the question I keep coming back to is - should I be prioritising getting more cardinals, neon and rummy noses to get their groups back to minimum size?

Or is this less important to fish who have been there since the beginning, are aware there is no threat in the tank, and are quite happy spending their days milling about solo anyway?

I like the rummy nose and cardinals but have found them to be sickly, so I'm not sure I want more.

[black ghost]

For me, 6 is not a group, it’s a poor compromise, because if shops tried to sell proper groups of 20 and 30 they wouldn’t sell many fish. Hardly any aquarists really go with what the fish would prefer, but at least the compromise of 6 means that most will keep the fish with a few of its own kind.

You make a valid point about the fish knowing that they’re safe. Some species need a group for its social structure, but tetras tend to need a group more for protection and security in numbers, so if they feel safe I don’t think it’s such a big issue that they’re dwindling.

It’s a quandary isn’t it? If you upped the numbers, only for them to dwindle again over time, it means you’ll always have to keep those species. I would probably leave them as they are if you’re not wanting to restock with the same species.

[Andys temperate tank]

I found the more rummie noses I added the better they shoaled/schooled.