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Discussion Starter · #1 ·
I often see anecdotes of people having egg-laying fish spawn and fry survive in large tanks - no separation of fry from parents involved. The kind of situation where there are more fish than were originally placed in the tank or small fish appear out of nowhere. I would love to have this happen down the line in my 120 gallon tank. I am fine with keeping limited numbers of species.

To those who have had such experiences - please describe your setups! Species involved, feeding regimes, tank size, etc.
 

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I've had this type of surprise happen a few times.


Once when we converted a marine tank with overflow and sump into a freshwater aquarium, I found healthy young fish down in the sump chamber and got a big surprise!


With Danios, it just happens, if there is plenty of plant cover and some moss in the tank.


One other time was when I found tiny little Columbian River tetras in my reasonably heavy planted tank down in the java moss. They seemed to be doing just fine; tank had been set up for maybe six months, and apparently they found plenty to eat. I did remove them after I found them to a spare 10 gallon and raised quite a school.


I doubt that it's uncommon to find a few survivors now and then in a well established, really heavily planted tank with plenty of cover and good water quality. I am guessing bottom dwelling fish would reduce these occurrences, but I haven't usually kept cories, etc.
 

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Discussion Starter · #3 ·
A lot of the anecdotes I see do involve danios. I guess they're just a prolific bunch of plants.

With your Columbian River tetras - was the tank six months old when you introduced them or found the fry? How were you feeding the adults?

Seems like moss is pretty helpful, as both a site for spawning/egg deposition and microorganism culturing.
 

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With the Columbian River Tetras, my memory is I found the fry 3 or 4 weeks after introducing the group of 6 adults to the tank. They were big enough to positively identify when I found them.


I don't remember feeding anything other than assorted flakes and possibly some freeze dried bloodworms or other treat. I don't think I was feeding live or frozen foods at the time, but it was quite a few years ago, so I am not positive. I do remember having some scuds in that tank, which were likely a feast for fry.
 

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How about Praecox Rainbows?

The group started at 10 about 3 years ago and it's down to 7 or 8 now....I think; These guys never stop moving.

The tank is a 25G or so Oceanic cube I got used some years ago. I built an open stand for it and the plan was to leave it open top and hang riparium baskets around the back rims. It perfectly fit an odd corner in the den. I only ran the smallest of the Rena Filstar canisters. It "was" a neat looking tank with a cool piece of cypress that I finally got to stay submerged. Some crypts and that was as far as I got. The tank ended up being a maintenance PITA. It's just extraneous and far from all my other tanks that have their own water supply lines, etc. So it's a VERY neglected tank. I was actually about to donate the fish and contents to a classroom project a couple of months ago and tear it down.

Until one day I scraped back some of the BGA off the glass and I could see the little ones swimming around. The only other things that have occupied the tank for the 3 years it's been there is a couple of Sterbae, two amanos and some snails.

There's about a dozen or so little ones in there and they are about 1/4 to 3/4" now. My guess is the canister flow got slow enough that these guys survived. The tank is far from densely planted.

I'm in the process of re-locating the fish room to the opposite corner of the basement (a painful exercise!), and this tank will move, intact and get its' first water change in a while. Just a sponge filter this time so we'll see if it happens again. The group was always "male-heavy", and with only one female left so I'm not that optimistic. But there's a batch of little ones that may do it in a year or so.
 

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Discussion Starter · #6 ·
Thanks for sharing. Rainbows are another fish I see this kind of thing happen often with, though the extent of which the parents eat the eggs/fry seems to vary a lot based on species or who you're asking. I've always like Pseudomugil spp. and threadfin rainbows. But I'm pretty open in considering species, as long as they do well in soft water and won't absolutely exterminate dwarf shrimp.
 

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2 inch thick carpet of baby dwarf tears and you will certainly raise the odd straggler. I think fry are most at risk in the wriggler stage.
If they get to do this in their own strata of the tank, it greatly increases their chances. Small fish, like danios', fry are pretty sharp once through the wriggling. They are very good at darting away from threats, considering how small their brains are. Leaf litter on the bottom could do a decent job of hiding small fry, but would suck at hiding the eggs.

If you want fry, I'd rather set up a small 10g fry tank, only filled half and let it cycle.
You can collect eggs virtually any morning from healthy danios.



Here I used a CD holder's cover, a piece of net, a rubber band, and some plants in the middle to make an egg collecting station.
The closer to the surface the less chance for the eggs to be eaten while they drop.
 

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It's amazing that any small egg-layer fry survive in a well stocked community tank. My 40 long had 3 Red Phantom and a 2 Lemon Tetra babies survive to ~0.5" size.

The odds of which were staggering in that there was a hungry school of 5 Flame Tetras, 4 full sized Bleeding Hearts and two smaller schools of the Lemon and Red Phantoms, and a mated pair of Golden Eyed Dwarf ciclids.

There was a forest of Rotala, and Hygrophila Polysperma, Java Fern and the bottom was a patchy lawn of Java Moss.

Egglayer fry, once they get into the free-swimming stage generally head to the water surface, because that's where most of the best food lives. Through luck or instinct, these babies manage to escape detection in the worst pace in a tank to 'not be seen'.

A lot of these fry have an instinct to hug close to plant stalks and shelter in the shadows of floating leaves, and or stick in close to the meniscus of the tank glass and water edge. Being small and nearly transparent has it's advantages.
 

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Fish in general like something to hide under, I float plastic tub lids in my more sparsely planted fry tanks.
They like hanging out under them like plastic lily leaves. I find it helps the shyer fishes to get their share of food if they feel safer.
 

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Some egglayer fry are better at it than others.

White Cloud youngsters tend to just start swimming out in the open, once they get an appetite, because their parents tend to not make meals of them. Tetra babies exploit all sorts of tricks to not be seen while out foraging, I've raised a few tankfuls of tetra fry, you really have to go looking for them even after 2 weeks of their hatching.
 

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Discussion Starter · #12 ·
Good point about fry behavior. I guess it's worth considering each species' fry habits, as my tank doesn't have any floating plants and pretty strong current at the surface. Definitely more than enough plants for them at the bottom and middle, but if they try to go right to the surface I don't think they'd last long. What are some groups of fish that tend to have more benthic fry?
 

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Good point about fry behavior. I guess it's worth considering each species' fry habits, as my tank doesn't have any floating plants and pretty strong current at the surface. Definitely more than enough plants for them at the bottom and middle, but if they try to go right to the surface I don't think they'd last long. What are some groups of fish that tend to have more benthic fry?
I've never known any of the tiny egglayer fry to spend much time on the bottom once free-swimming and hungry. When they get more motile and bigger sized, if they prefer the bottom, they'll spend more time there. Probably exceptions to this rule, I've never encountered it. Dwarf Ciclid babies, if not being escorted by their parents tend to hug the bottom and plant tangles. And Cory catfish babies also lurk near the bottom.

When my Goldeneye Dwarf Ciclids spawned, the female took the youngsters out for their first 'stroll' around the 45 gallon tank. Goldeneye free-swimmers are really cohesive, they stay exactly under Mom, and hug the substrate and any surface she swims over, like a living magic carpet.

It is really mesmerizing and a little weird looking. From distance it looks like the female is escorting a bright oblong around the tank. Mind you there were a few bigger, dither tetras that were slyly stalking this group. They soon discovered how freakishly psycho a female Goldeneye is with her kids.
 

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My metae cories regularly spawn and if I have enough cover in the tank, the babies regularly make it to adult size. I often see many eggs laid, but I think a lot get eaten before hatching. I have a thick forest of echinodorus "xingu" and I find the fry mostly in there. Not too many other places to hide. Tankmates are an angel, tetras, snails, otos, a clown pleco, and a 21 year old spotted Raphael. Nothing special about my setup, pH 6.2, GH 3 temp 78. I feed an assortment of dried foods, with occasional frozen. Like I said, when I let the chain swords grow, the cories just appear. No cover=no fry.
 

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I actually found one cory fry in the tank the other day, about the size of the largest ones I have in the breeding net that I raised from collected eggs. I have enough fry now, that I take maybe 3 or 5 eggs off the glass now when I see them, and let them eat the others to stay in good condition.
 

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Just wanted to add.... I need not be a large tank. My experience was with Zebra Danios in a 10 gallon tank on my bedroom dresser. Planted tanks provide lots of cover. I used to feed the occupants regularly so I believe they were less inclined t feed the young. I had an air operated sponge filter running in conjunction with an air powered UG filter. So the fry were not hurt by being sucked into the filter. One day I noticed the small fry swimming around and quickly started feeding microworms.

I have only had this happen in single species tanks though... I wonder if different species are more likely to eat the fry of other species....

Bump: Just wanted to add.... I need not be a large tank. My experience was with Zebra Danios in a 10 gallon tank on my bedroom dresser. Planted tanks provide lots of cover. I used to feed the occupants regularly so I believe they were less inclined t feed the young. I had an air operated sponge filter running in conjunction with an air powered UG filter. So the fry were not hurt by being sucked into the filter. One day I noticed the small fry swimming around and quickly started feeding microworms.

I have only had this happen in single species tanks though... I wonder if different species are more likely to eat the fry of other species....
 
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