I think my Cardinal tetra is old…

Magnum Man · Jun 13, 2026

it’s been here for a little over 2 years, but arrived in a group of “jumbo’s”, that I tried, when the angel fish in that tank ( to my horror) actively hunted a dozen and a half run of the mill sized Cardinals… he seemed to leave the 8-10 jumbo size alone, but adding more proved difficult… I don’t know where the jumbos come from, I don’t think they were wild caught, assume they were old breeders rotated out from a fish farm???

… the angel has been long gone, and slowly the group of jumbo’s gradually grew smaller until there was just one, and it has been swimming with a single rummy nose, that out lasted the rest of it’s group… for 2 years, it’s been the only cardinal in this tank… lately it’s not been hanging with the rummy nose, and is much less active… I didn’t see it for a couple days, and being the only, it was missed… I see it this morning, still swimming normal, just much less active than it used to be… with a fish like this, I have no idea of it’s age, but suspect it nearing the twilight time???

btw… a new group has been on my buy list for a while, since the angel is gone, they’ll be the normal size, but with retirement, and Mrs. illness I’ve not ordered fish for a while… it’ll be sad, if he doesn’t get to be the king of a new group, before it dies…

GaryE · Jun 13, 2026

I was surprised by cardinal growth rates when I bred them. The small ones we buy are around 3 months old. The wild caught ones I got this week are 4-5 months, by their size, but they sat at the store for 6-8 weeks. He brought in a couple of thousand, apparently, and while they sold well as always, just the numbers kept some there. My one year olds are about 80% of the size of my 3 year olds. I didn't expect the ones coming in small to be THAT young.

I try to avoid 'jumbo' anything, though I can see why you didn't. I hate it when a shipper sends me full sized adults, because you can't know their age With cardinals, I suspect most are bred by farms at one to two years old. Then they unload them.

We can be frustrated waiting for young fish to develop their adult beauty, but it's worth it. I got some Iriatherina werneri (threadfin rainbows) a few weeks ago, and I've only been able to sex them for about a week. But it's nice to watch the fins grow and the colours kick in. There's nothing in their tank that will eat them, a key consideration.

bgarthe · Jun 13, 2026

I agree and prefer to buy on the young side. I am really enjoying watching several tetra groups and my 2 Angels (in separate tanks) grow up, especially my Congo Tetras. I did have to get tweens of Congos so I could ID males. Now they’re really coloring up, getting to adult size, and those fins are exquisite as they grow out.

My 36 Cardinal Tetras are all still on the youngish side at around an inch each. My two older ones are bigger/fuller bodied being 2+ years old. I got green neon tetras almost 3 years ago that were about 1/2” long and now they’re grown up doing great.