Baby fish!!

[AdoraBelle Dearheart]

<Snipped for space useful and very accurate info about livebearer math>

It's this very math that often leads to some big problems for beginners to the hobby, soon overwhelming them. When the problems caused by overstocking/buying more tanks to try to raise all the fry and soon being overwhelmed/having a hard time finding any store willing to take them off your hands/trying to sell them privately which is a time-consuming hassle and a Sisyphean task when you have hundreds of young starting to breed themselves at three months old and people only want 3-4 guppies they've picked out themselves...


Guppies are nicknamed "the million fish" based on this, and just how quickly the numbers go up. Breeding them can be a lot of fun! Especially when you have a local store that's happy to take the young, as mine did, but even then I needed to have multiple smaller tanks to raise them to three months old and were a sellable age and size first, and with several females having batches most every month, you have a lot of batches of young to handle, and can't really do it without multiple tanks to sort by sex, which means a lot more maintenance and faffing about, and not the simple beginners fish tank many hoped for when they started. Or, they stick with one tank, the numbers multiply rapidly and the tank becomes overstocked, eventually leading to poor water quality and sadly fairly often, a tank crash that wipes all of their fish. Which is a horrible thing to go through, makes people feel guilty and sad, and then all too often give up the hobby after something like that.

We warn you of this not to scare you or put you off - quite the opposite. It's a heads-up so you can plan now what you need to do in order to avoid any of the above fates and keep a healthy tank of fish the way you want to, and thereby hopefully more fish-keepers remain in the hobby! It's so you can take a look at how many female livebearers you currently have, you can be prepared in advance and talk to local fish stores to see if they're willing to take fry when they're old enough, to give you a chance to look into whether you want to set up a nursery tank for the fry to grow in and can check out livebearer breeders set ups and see what you want to aim for, or if you'd like to breed and raise fry for a while, keep one or two female livebearers, return/rehome any others, and so you'll know in advance that even if separated from the males, female livebearers will still be storing the sperm packets from previous matings and continue popping out batches of fry for a long time. Several months, even up to a year.

Knowledge is power. We warn you because we've been there ourselves, and many people come here with the same potential problems, but they're already at the stage where they've become overwhelmed by the numbers, are losing fish because the tank has rapidly become overstocked, the water quality went down and the tank crashed; becoming an emergency situation that's much harder to resolve and heart-breaking to go through. But if you warn you now about the above issues, you're at a good time to assess your current stocking, tank, and time availability, and be prepared to head off trouble at the pass.

We would much rather help guide people to have healthy, beautiful, successful tanks so that they join our fishkeeping cult remain in the hobby and love it as we do, rather than the above crisis points happening where it's much harder to help talk them through the problems at a distance online when it's an emergency, fish are dying, and they end up giving up the hobby altogether, which sadly happens all too often. But forewarned is forearmed, and we're always knocking around here somewhere and happy to answer any follow up questions or worries you have!

 

[Ichthys]

Livebearer tanks do not become overstocked. There have been scientific studies that showed it. They reach an optimum bioload and then it stays the same. Fewer fry are born, fewer live, adults die younger, etc.

Also, being pedantic, only egglayers spawn.

 

[AdoraBelle Dearheart]

Livebearer tanks do not become overstocked. There have been scientific studies that showed it. They reach an optimum bioload and then it stays the same. Fewer fry are born, fewer live, adults die younger, etc.

Also, being pedantic, only egglayers spawn.

This is an interesting angle I've never heard before! Can you link any of those scientific studies, please? I would sincerely love to see them.

 

[emeraldking]

Livebearer tanks do not become overstocked. There have been scientific studies that showed it. They reach an optimum bioload and then it stays the same. Fewer fry are born, fewer live, adults die younger, etc.

True! It stabilizes at some point. But what most people mean by this overstocking is more when the body size per fish is in agreement with the space in the tank.
I do get it what you mean. For I've got a lot of breeding tanks. And to most people, they'd be overstocked. But like you have already have claimed, it stabilizes. Mother Nature is taking care of it. If it really becomes overcrowded, a number will die to get it stable again. Or the batches of fry become less.

Also, being pedantic, only egglayers spawn.

Correct! But a lot of members overhere use it as a matter of speech.

 

[AdoraBelle Dearheart]

This is an interesting angle I've never heard before! Can you link any of those scientific studies, please? I would sincerely love to see them.

True! It stabilizes at some point. But what most people mean by this overstocking is more when the body size per fish is in agreement with the space in the tank.
I do get it what you mean. For I've got a lot of breeding tanks. And to most people, they'd be overstocked. But like you have already have claimed, it stabilizes.

Again, would appreciate it if either of you could link to some scientific papers about this.

Mother Nature is taking care of it. If it really becomes overcrowded, a number will die to get it stable again. Or the batches of fry become less.

Mother nature is wonderfully complex and takes care of many things, however, mother nature is somewhat interfered with when we're taking mass-produced, often sickly and weak human-bred fish and sticking them into tiny glass boxes then expecting mother nature to handle it the same way she would in a river or lake. We're creating artificial environments and are responsible for the lives of the creatures we choose to acquire and throw into those glass boxes together. Leaving the tank to become overcrowded and allowing fish to die and just shrugging it off isn't really the goal we're aiming for when we're advising people who are new to the hobby and just want a peaceful, pleasant community tank, not an overstocked one with fish dying off to make room and potentially polluting the water, leading to an ammonia spike, cascading problems as the ammonia builds and more fish die, and they don't know what's happening or how to fix it.

You two know how to manage an overstocked tank so the fish aren't being poisoned by ammonia/high nitrates thanks to your knowledge levels and experience in the hobby with managing overcrowded/overstocked tanks. But we're trying to help a beginner here with their first fry, so surely you see how quibbling over the difference between a tank being overcrowded vs overstocked, when the potential hazards faced by a beginner who has their first female livebearers (and we don't know how many they have, tank size or if they have spare tanks/knowledge of the cycle) of how to avoid the water quality becoming poor as the bioload increases, or what to do with the spare fish being produced in their overcrowded/over-stocked tank is still a problem they will have to deal with fairly rapidly now that fry are being produced?

Correct! But a lot of members overhere use it as a matter of speech.

It's also easy for someone to have a slip of the tongue when they're used to breeding egg-layers and that isn't the thrust of their comment. Just seems a petty correction when I know full well that @TwoTankAmin is fully aware of the difference between egg-laying and live-bearing fish. Just like when a beginner comes here to ask if their fish is pregnant, I'll use the term gravid, but rarely say "actually, fish are not mammals and cannot be pregnant, the term is gravid since they're hatching eggs internally then birthing the fry live". Because it's being petty, not important to the point of the comment, and people who dive deeper into the hobby soon learn the difference anyway. So the point is to help them and give the relevant and important info, rather than correct someone's typos, slip of the tongue, or minor mistakes in language.

If I'm mis-reading this because I'm grieving and angry, then I apologise. But this comes across as such fish-snobbery to me, and really put my back up. But I'm aware that I'm not in a good place and could be misinterpreting, and would still genuinely like to see some of those scientific papers, for my own further learning.

 

[emeraldking]

If I'm mis-reading this because I'm grieving and angry, then I apologise.

But we're trying to help a beginner here with their first fry, so surely you see how quibbling over the difference between a tank being overcrowded vs overstocked, when the potential hazards faced by a beginner who has their first female livebearers (and we don't know how many they have, tank size or if they have spare tanks/knowledge of the cycle) of how to avoid the water quality becoming poor as the bioload increases, or what to do with the spare fish being produced in their overcrowded/over-stocked tank is still a problem they will have to deal with fairly rapidly now that fry are being produced?

That's why I've written these lines as well...

But what most people mean by this overstocking is more when the body size per fish is in agreement with the space in the tank.

But a lot of members overhere use it as a matter of speech

 

[TwoTankAmin]

I think for the exact meaning of spawn, it depends on whether it is used as a verb or a noun. As a verb it means to release of deposit eggs which livebearers do not do.

However, as a noun it refers to eggs of fish, frog etc. And in that case the female livebearer carries a spawn inside her where the eggs grow to free swimming and she releases them. Also called giving birth by most.

Also, when I was keeping Montezuma swords, I did so in a well planted 20l mostly. The first fish would spawn and I would get a bunch of fry. Many survived by hiding in the plants and this even though Montys are know as fry eaters, most of the 1st fry would not be eaten. But then came a second and a third spawn. And by then the first spawn was large enough to eat the newest fry but still small enough to navigate the plants to find their relatives for lunch.. The adults kept making lunch for the first couple of spawns. However, by then I had removed offspring to send to others. However, I have no evidence that they were not continuing to breed more food for the most part.

Montys are also the only sword I have kept that sometimes stoped spawning for a while and then resumed doing so.

I am not so sure about what accounts for the "stabilizing" reported above. My hunch is that a build up of hormones or other chemicals may signal the fish to stop spawning as much. Or maybe it actually inhibits spawning and/or causes egg production to be reduced. I would bet the place to ask about this might be here:
Xiphophorus Genetic Stock Center

 

[Ichthys]

This is an interesting angle I've never heard before! Can you link any of those scientific studies, please? I would sincerely love to see them.

I can’t, I’m afraid. Maybe emeraldking can. I read a paper a long time ago (about 20 years?) but have never been able to find it again since.
Here’s what I remember…
They set up about 20 identical tanks (identical in every way - it was a scientific experiment). Into each tank they put different numbers of guppies, from two (a pair) to 100. After a few months every tank had the same bioload (about 50 fish).
In the tanks with fewer than 50, there were many fry, they grew fast, adults grew big and lived long, etc etc, until the optimum bioload was reached.
In the overstocked tanks (more than 5Oish fish) either no fry or not many were born, and adults died young to bring the bioload down.
Once the optimum bioload was reached, all tanks, iirc, saw fry born and surviving only to replace the losses, and no more.
(I took a leap to say it’s true for all livebearers. I’m pleased emeraldking confirmed my leap. )

I think it actually happens with a lot of fish, egglayers included. If a body of water dries up and reduces in volume significantly, the fish will adapt by staying smaller, breeding less, etc. I know it happens with at least some very prolific cichlids, such as the tilapias.

 

[vio88]

I accidentally killed off my guppy fry the first time. I was feeding my fish flake food and didn't realise I needed to crumble it to powder for the fry to be able to eat it. Its kind of a cruel thought but may be a way to prevent over population.

 

[TwoTankAmin]

Basically, the explanation makes a bit of sense. If you live in a garbage dump you die young. If you live in a garbage dump you eventually stop reproducing. So, the tank may become what some call stable but I would call it a garbage dump.

The first fish which reproduce for me for me that were not live bearers , they were common tanks strains of bristlenose. I had long finned ones in my 45 gal. planted community. I never knew they were spawning because the fry were eaten very fast. And then one day I spotted a fry. I am not sure if it was a good or bad thing, but I had been buying some fish from a breeder and he convinced me to pull the cave with the dad and raise the fry. In exchange I convinced him to try some live plants which he did not do at al until I sent him some.l.

While bn are not livebearers, they try to compete with them for reproduction awards. I was overrun by them for years. I actually had bn in grow tanks go down the uplift tune of a sponge filter and spawn inside.

I had babies in the breeding tanks, in the community tanks and in grow tanks. As I wrote elsewhere, my final spawn from bn was over 100 eggs. And then I took all of the bn I had to one of Catfish conventions and sold them all (about 50 fish) for $70 to somebody who worked in a store.

All of the above taught me that the more fish I had in a tank the worse it became for everyone there. The fish grew more slowly, there was a lot of aggression, especially at feeding time. I quickly learned to set up more tanks and then to put fry eaters in with the bn. That was a far better solution that letting the overcrowding close down spawning by making the tank way less healthy that I wanted it.

Today I do not keep bristlenose I do not keep angels what I could have spawn (only Altums). I no longer get spawning that live from most of my fish besides the plecos. And the ones I keep average under 20 eggs in a spawn and are more likely to be a 15 or fewer, I still struggle at times to move them all out. During the 2020 year Covid shut down most of my sales. No events to attend, no club meetings and nobody allowed to come to the house to buy fish. I am still struggling a bit today to work off the excess since the fish did not stop spawning during that time.

Anecdotally speaking, I beleive that when there are few or no fry on a tank, the fish spawn as expected. When there are fry building up in the tank they continue. But plecos will go on hiatus now and then which means no new fry for a while. Most livebearers do not do this under normal conditions. However, If I do not move pleco offspring to new homes a build up will cause all sorts of issues.

If nothing else, I have learned that overcrowding fish beyond a given point works to make things decline. I get fewer spawns, I may start to see deformities and if I am not careful; I could allow for more serious issues. What keeps me on the straight and narrow is that I pocked very expensive fish with which to fall in love. Nobody wanted common livebearers, few folks wanted to buy 14 or 20 bn at a go but if I lost them all it was not a financial disaster. However, with pricey plecos it is another story. So there is excess motivation to keep them healthy.

Because I use species tanks. there is no fry predation. Hypancistrus do not eat their own kind.

However, because I like to look for the science I have started to search for studies on livelbear population size in capticity and what effects there might be. I quickly found one study using least killies it is not quite dead on the mark, but there are some interesting observations which do relate to this topic. Maybe we need a new thread for that discussion?

BAER, C., TRAVIS, J., & HIGGINS, K. (2000). Experimental evolution in Heterandria formosa, a livebearing fish: Group selection on population size. Genetics Research, 76(2), 169-178. doi:10.1017/S0016672300004687

https://www.cambridge.org/core/jour...ulation-size/281DDBE405A3757BDB31C8CD3B17244E

I will keep looking for more. There are out there. Here is one more which looks at using "good" bacteria to make crowded tanks more healthy.

Ghosh, S., Sinha, A. and Sahu, C., 2008. Bioaugmentation in the growth and water quality of livebearing ornamental fishes. Aquaculture International, 16(5), pp.393-403.

Abstract Bacillus subtilis isolated from the intestine of Cirrhinus mrigala (Hamilton) was incorporated into the rearing water of Poecilia reticulata (Peters), Poecilia sphenops (Valenciennes), Xiphophorus helleri (Heckel) and Xiphophorus maculatus (Gunther) at four different concentrations (5 9 108 cells ml-1, 5 9 107 cells ml-1, 5 9 106 cells ml-1 and 5 9 105 cells ml-1) and its effect on fish growth performance and survival, water quality parameters and bacterial population of water were assessed. The results showed that the addition of bacterial cells in the rearing water resulted in greater survival and a faster growth rate and, hence, greater length and weight increments of the livebearers. The use of a bioaugmentor in the rearing water of the livebearing fishes resulted in significantly lower (P \0.05) concentrations of dissolved organic matter and total ammonium nitrogen. The counts of motile aeromonads and total coliforms recorded in the water of bioaugmented tanks were also lower than that in the control tank. Bioaugmentation between 106 and 108 cells ml-1 in the rearing water is sufficient in establishing a bioaugmentor and the use of a higher concentration of bacterial cells did not always lead to significantly better
results.

What the above indicates is that overcrowding without measures to counter things will result in less healthy fish.

edited for spelling, typos and grammar.