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About two weeks ago I went to check on my C. sterbai fry. They are in a 10 gallon tank and were placed there as eggs. As the lights were out, I used a flashlight and immediately noticed three tetra fry swimming about! Strange, but maybe I transferred some Java moss with tetra eggs to the grow out tank?

I have one 40 with black skirt tetras, but they seem to me too young to spawn. There is another 40 with a school of silver tip tetras.

Yesterday, I decided to upgrade my blackwater maker tank from a ten to a 20 long to have more blackwater on hand. The tank was stuffed with driftwood and leaves to the top and only filled with straight rainwater collected from an outdoor rain barrel.

I drained about 80% of the 10 gallon and transferred the water, driftwood, and leaves to a 20. This morning I did a quick tank check and swimming in the former blackwater 10 was a single tetra fry! I can not begin to imagine how it got in there nor imagine how it survived in pure rainwater. Not to mention me, every week, taking out 70% of the blackwater and replacing it with water from outside at 40F (4.4C)!

There is a logical explanation I am sure, but how that fish got into that tank and survived is baffling.

-Shane

If it's a black skirt tetra fry then I do know they can take cool water, and I guess eggs are hardier than fishes in clean water. But it's still a long shot!

Jools

Last night I discovered another two tetra fry in the (what I thought was empty) 10 gallon I spawned the C. sterbai in. They are larger and are clearly black skirt fry. Your thoughts on black skirts handling low temps makes sense given their origins in the far south.

Now how in the heck did I spread tetra fry to three separate tanks and why can't I do this with say Mystus or Hypancistrus
-Shane

Shane wrote: ↑10 Jan 2021, 19:23why can't I do this with say Mystus or Hypancistrus

Perhaps because you don't have any? (Hint Hint).

On the tetras, shared siphon tube, net or bucket when cleaning out?

Jools

On the tetras, shared siphon tube, net or bucket when cleaning out

Per Occam's Razor, this would be the most likely answer. Sites say a big black skirt female can lay 1,000 eggs. My small females may be each laying several dozen that end up in the bottom of the bucket and are transferred when I use those buckets on the next water change or fill them with rain water from the rain barrel.

Regardless, I am clearly in the tetra spawning business. Even if by accident.
-Shane

Let me throw in another twist. I do not think these are silver tips or black skirts. Eggs on a purchased plant seems to be the only answer... I have now counted 7 of these spread over 3 tanks.
-Shane

Wow, that's interesting! ahahaha a strange situation, I myself wonder how it happened

MY vote goes to they came in on plants. My second tank was set up because I had swordtails in my first and got too many fry. I also had zebra danios, rosy barbs and cirys. I set up the new tank and moved plants from the established tank. I was dosing this new tank with ammonia to get it cycled. One evening I went to add ammonia and I saw movement. There were two tiny fry in the tank. I had no clue what they were, but I did stop adding ammonia. Turned out they were zebra danios.

Here is a song for this https://www.youtube.com/watch?v=X68J4esdA38

Great song!
Plants were bought through my local club (which is why they were not washed). Should be easy enough to track down as I bought a bag of Java moss from one member and a bag of Christmas moss from another. My best guess at an ID would be black phantom tetras, but I am no expert. I'll grow them up and replace the silvertip tetras. Those things pretty, but are rotten little suckers that just attack each other non stop.
-Shane

Shane wrote: ↑22 Jan 2021, 22:52Plants were bought through my local club (which is why they were not washed). Should be easy enough to track down as I bought a bag of Java moss from one member and a bag of Christmas moss from another.

Personally, a fish hitchhiker probably wouldn't bother me (although I've never seen L046 hitchikers - in my experience the hitchhiker eggs are always of tetras or barbs if they're fishes). But what chaps my hide is when I buy plants at a fish club or even a LFS and find them contaminated with snail eggs. If those hatch in my tank, dang those snails are hard to get rid of after-the-fact (I've developed a few tricks, but none 100%).

So as not to be guilty of the same thing in reverse, when I sell Java moss at my LFS, I will fill a bag with about 2 cups or more of Java moss, and I label my bags "Snail eggs. May include Java moss." Most people get the joke, but the first time I did that, the club auctioneer said aloud to the audience, "I think this bag is mislabeled. I think it's supposed to say 'Java moss'."

Sometimes my humor falls flat.

Cheers, Eric

Eric,
The humor is not lost on me. After buying the plants I now have pond snails and trumpet snails....
-Shane

Well the mystery just gets more bizarre. The original 6 tetra fry have grown out well and I'll post a pic looking for an ID.
Three days ago while checking on the 10 gallon cory grow out tank I noticed 6 more tiny newborn tetra fry in the tank! They appear to be the same sp as the original batch but showed up 6 weeks later. If these eggs came in on a plant, what have they been doing for the last month and a half?
I am at a complete loss to come up with a logical explanation as nothing has been in that 10 gallon tank but cory fry for two months and nothing new (plants, substrate, filter, etc) has been added. So now I have had two groups of tetra fry show up over 6 weeks from a tetra sp I do not have anywhere in my fishroom.
-Shane

Ooooooh, the mystery deepens! My curiosity is piqued, waiting for a resolution. Please keep the photos coming as the babies grow.

Cheers, Eric

Pics of the only 2 tetra spp in my fishroom.
Oldest tetra fry.
Newest tetra fry (left of cory fry).

I am not complaining about the "free" fish, but wish I knew where they are coming from!
-Shane

Have you considered that you might be having late night visits from the fish fairy?

You oldest baby reminds me of something similar to a serpae tetra (not a great match, but similar). Maybe serpae tetras are the product of silver tip tetras and black skirt tetras! (JK)

Shane wrote: ↑08 Jan 2021, 16:23Yesterday, I decided to upgrade my blackwater maker tank from a ten to a 20 long to have more blackwater on hand. The tank was stuffed with driftwood and leaves to the top and only filled with straight rainwater collected from an outdoor rain barrel.

Maybe a mischievious neighbor is seeding your outdoor rain barrel?

Cheers, Eric

Update on the mystery tetras. There are 12 total. Any tetra experts with an ID?
-Shane

I am no tetra expert, but ? Anyway, well done on getting them this far.

Jools

That is the identification I was leaning towards. I caught the original six and the second batch of six and moved them to a 40 breeder. As I cleared out the tank with the second batch I came across a single fry about half the size of the other six. I have watched that ten gallon for hours and counted the fry repeatedly so I am baffled again how a tiny 7th fry showed up. Looks like I'll end up with 13 tetras assuming the spontaneous generation stops. And to be clear, if anyone told me this was happening in their fishroom I would tell them they were imagining things.
My wife and I have two competing theories. She thinks the first batch of six fry spawned the second and third batches. This would require them to spawn at less than .5 inches. I think that all the eggs came in together but for some reason they hatched at different times with some hatching immediately and others laying dormant. I'll have to see if there is any research on the delayed hatching of tetra eggs.
-Shane

I never heard of any tetra laying eggs being only 1 cm. Therefore this explanation of what happened cannot be right. But, on the other hand, delayed hatching is also not something commonly found.

You did rule out any chances of having acquired the eggs twice? Than delaying hatching must be what happend. Perhaps different hatching temperatures did have an influence? For instance keeping them cold.

Yes, I only bought plants once back in December. First six fry showed up in early Jan, second six in early Feb, and I just noticed a single new fry on 22 Feb. It appears to be 10-14 days old. Plants would also explain the fry turning up in three different tanks.
All the tetra fry are in their own 40 gal and the C. sterbai fry are all in another 40 with their parents. Yesterday I placed a trio of Otocinclus in one 10 gallon and six C adolfoi in the other 10 gallon as those are my next spawning projects. We'll see if any more tetra fry appear.
Cold temperatures could be the factor. The tanks were hit with large cool rainwater changes several times in an attempt to get the C. sterbai spawning.
-Shane

Well C. adolfoi did not prove a challenge. Transferred out 9 eggs today. Dropped another half dozen in the tank trying to remove them. I am really bad at harvesting Corydoras eggs. Added a yarn spawning mop to make things easier in the future. Incubating the eggs in the tank with the tetra fry.
-Shane

Congratulations. If the eggs are on glass, the easiest thing to do is a partial water change - lower the water level below the eggs and scrape them off with a razor blade. You can also do this under water, but if the eggs are old enough to have lost their fresh stickiness, then they'll just sink to the bottom as you loosen them with the razor.

Good luck,
Eric

I'll give that a try. Great idea Eric.
-Shane