How long until fry are fully grown?

[Jack TH]

Hey all.

I have 12 yellow micariff-endler hybrid fry in a 5 gallon. I used to feed them finely crushed flakes and daphnia but I have recently decided to start feeding them specialised fry food. They seem to be growing faster with it.

They are about 2 months old. I'd say they are about 50% the length of an adult. Some are starting to get bigger than the others, and are starting to show colour on both the tail and the body. I'm guessing these ones are the males that are starting to sexually mature. Once I start seeing gonopodium development, I will separate the male fry from the female fry to stop breeding.

So onto my question: How long should it take for them to fully grow? I want to wait until the females are at least 95% grown, as I want there to be a good fry yield and I want there to be as few side effects from birth as possible. Their mother had good genetics when it comes to this, she was still perfectly formed after giving birth to the little ones, so I'm hoping to minimise the risks as much as possible.

 

[Colin_T]

Under ideal conditions they should be sexually mature at 3 months and full grown at 6 months, however they don't normally grow under ideal conditions and can take twice as long if not looked after properly.

If you want to breed the females then let them mature before breeding. Try not to breed the females until they are at least 6 months old.

Do big (75%) water changes each day to help reduce growth inhibiting hormones.

Keep the temperature around 28C (82F) while the fry are growing.

Feed the fry 4-5 times per day on a variety of food including newly hatched brineshrimp and fresh or frozen (but defrosted) foods that the adults get. Just cut the food up finely so the fry can eat it. You want the fry to be full of food and look like a fat pregnant female guppy.

 

[Jack TH]

If you want to breed the females then let them mature before breeding.

I'm planning on doing this.

Try not to breed the females until they are at least 6 months old.

I don't know whether I can stick to this. I guess I can choose good females at 3 months and keep just them in the 5 gallon, as well as the male I decide to breed until 6 months of age. I'm planning on transferring most if not all of the females I decide not to use for the next generation into the main tank as I have a female shortage at the moment.

Do big (75%) water changes each day to help reduce growth inhibiting hormones.

I don't know if this is necessary, because I don't have any adults in with them. I separated the mother when the fry were born.

Feed the fry 4-5 times per day on a variety of food including newly hatched brineshrimp and fresh or frozen (but defrosted) foods that the adults get

They seem to grow faster on the specialised fry food than the freeze-dried food. I haven't tried live food because I can't find any anywhere. I'm gonna stick to the fry food for now, if their growth stalls then I'll try getting some live food.

You want the fry to be full of food and look like a fat pregnant female guppy.

Check, they look like they are about to burst after every meal.

 

[Colin_T]

You want to separate the males and females as soon as you can. Then keep the females away from all males until the females are 6 months or older. Then put a male in with the females. If you keep young males with the females they will breed and the females will be more likely to have pregnancy issues due to being young.

When breeding livebearers, you want tanks for males, tanks for females and tanks for breeding them. Basically keep all males in one tank, all females in another tank and put a female and male together in a breeding tank for a week and then move the adults back into their male or female tank. This stops the males breeding with all the females and reduces stress to the females by the males constant harassment.

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The growth inhibiting hormones are produced by baby fish to slow the growth of other baby fish around them. The big daily water changes are used to dilute the hormone in the water so all the fry grow at a more even rate.

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You can buy dry brineshrimp eggs at most petshops or online and hatch the eggs in salt water. Then feed the newly hatched shrimp to baby fish. There is more info on live fry foods at the following link.
http://www.fishforums.net/threads/back-to-basics-when-breeding-fish.448304/

 

[Jack TH]

If you keep young males with the females they will breed and the females will be more likely to have pregnancy issues due to being young.

Well aware of this, like I said I'm planning on doing this, since I want to select who breeds with who.

When breeding livebearers, you want tanks for males, tanks for females and tanks for breeding them. Basically keep all males in one tank, all females in another tank and put a female and male together in a breeding tank for a week and then move the adults back into their male or female tank. This stops the males breeding with all the females and reduces stress to the females by the males constant harassment.

Well aware of this.

The growth inhibiting hormones are produced by baby fish to slow the growth of other baby fish around them.

I hear conflicting things about this 'growth inhibiting hormone'. One the one hand, some people say it's produced by adults, but on the other hand you're saying it's other fry that produce it. That doesn't make much sense to me because wouldn't the fry be stopping itself from growing by releasing it into the water? I've come to the conclusion that this hormone that fish supposedly produce doesn't actually exist. I've asked everybody who has told me about this 'hormone' if it's ever been identified and named and I've never got an answer. I don't think anyone knows because it's never been identified, simply because it's not a thing. I think it's normal for some to grow faster than others anyway, especially males growing faster than females. Also as well, take for example Kaimuki Backyard, his fry grow stupendously quickly yet he does changes about once a week. Can you please explain that one to me?

You can buy dry brineshrimp eggs at most petshops or online and hatch the eggs in salt water. Then feed the newly hatched shrimp to baby fish. There is more info on live fry foods at the following link.

Ok, I'll have a look.

 

[Colin_T]

I don't know who Kaimuki is.

The growth inhibiting hormones are produced by all young fish and are designed to inhibit the growth of other fish immediately around them. In a large water body like a river or very large aquarium, the hormones are diluted and washed away. However, in the confines of a small aquarium, the hormones can build up and slow the growth of all the fry in the tank.

The amount of hormone released is tiny and if you only have a few young fish in a 10 gallon tank, it will take a week or more for the hormone levels to build up to such a degree that it inhibits the fry. However, if you have 100 fry in a 10 gallon tank, each fry produces the hormone and the level increases much more quickly and it gets to a higher level because the fry are constantly producing it. In this situation all the fry in the tank will have slower growth because of the hormone. Big daily water changes will dilute the hormone so all the fry can grow faster.

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There have been studies done years ago and my own research into this showing a clear difference in growth patterns between fry reared in tanks that got regular water changes vs occasional water changes. In my tests I had 4 glass aquariums that were 2 foot long x 10 inches wide x 12 inches high. Each tank had about 10mm of natural brown gravel over the bottom, a 100 watt aquarium heater set to 28C, a floating glass thermometer, a corner sponge filter and an airstone bubbling away in the corner. The tanks had coverglass and a light unit above them. The light was on for 16 hours per day. There were no plants in the tank and algae grew on the glass.

I bred rainbowfish and other species including barbs, tetras, cichlids, labyrinths and catfish, however for the experiments I used Australian or New Guinea rainbowfish or ruby barbs (Pethia nigrofasciata). I bred a species of rainbowfish (eg: Melanotaenia trifasciata from the Goyder River) and reared the fry up for the first 2 weeks in the breeding tank. I then separated the fry into even numbered groups and put each group into their own 2 foot tank. On average there were about 20-30 fry in each tank. Some of the tests had 50-100 fry per tank but it depended on how many eggs were produced by the female or if I used several females in the breeding tank.

The fry were all fed 4-5 times per day with the same food at the same time. Initially brineshrimp nauplii and microworms were fed and as the fry grew, additional foods like marine mix (prawn, fish, squid & spinach blended up and mixed together) were offered. Fry were fed as much as they could eat and then extra brineshrimp nauplii were added to the tank and were left to swim around until eaten.

Tank 1 got a 50% water change each day.
Tank 2 got a 50% water change twice a week.
Tank 3 got a 50% water change once a week.
Tank 4 got a 50% water change once every 2 weeks.

The water was aged for a week in a holding tank with an undergravel filter, and had a general hardness of about 300ppm and a pH of 8.4.

The fry were kept in these tanks for 3 months at which time they were removed and the larger fry were sold to petshops.

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The experiments showed that fry getting frequent water changes (2 or more times per week) grew faster and to a bigger size during the 3 month period compared to the fry that got water changed once a week or less. These faster growing fry were sexually mature at 3 months and were more than half their maximum adult size. eg: the adult M. trifasciata rainbowfish grew to 100mm long and the 3 month old fry were around 60-65mm long, with the females being slightly smaller than the males.

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With the aquarium that was water changed once a week, the fry grew at a steady rate but only reached 40-45mm in length after 3 months. The fry were also sexually mature and males and females could be easily distinguished.

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With the tank that was water changed once every 2 weeks, the fry grew slowly and only reached 25-30mm in length after the 3 month period. These fry were not sexually mature and still looked like juvenile fish with silver colouration on their bodies and they exhibited no sexual dimorphism. There was a noticeable growth spurt within 48 hours of water changes done on this tank and then growth appeared to slow or halt until the next water change 2 weeks later. Growth was measured by photographing the tank from the same position each week and fry measured on the images, with estimated growth being approximately 2mm per week, most of which occurred in the first week after the water change. From the photographs there appeared to be no increase in size during the second week.

After the 3 month period, the fry in this tank were given daily 75% water changes and their growth accelerated. 6 weeks later these fry had changed colour and now showed sexual dimorphism and were approximately 60mm long. They were then sold to shops.

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I repeated this experiment a number of times using different species of rainbowfish and barbs and the results were always the same.

I did the same experiment using cooler and warmer temperatures. The rearing tanks were fed the same and got the same water changes as mentioned above. Fry living in rearing tanks kept at 22C, 24C & 26C grew slower compared to fish in warmer water. Fry living in tanks kept at 30C did not grow any faster than fry living in tanks kept at 28C. I found 28C to be the optimum temperature for rearing most tropical aquarium fish during the first 3 months of their life.

Food was another thing I tested with fry being kept at the same temperature and getting the same water changes and the same type of food. The fry were fed the same number of times each day, but some tanks were given more food than other tanks. The less food they got, the slower they grew. Fry that were not fed a lot of food but were given regular water changes, did continue to grow, albeit at a slower rate than fry fed more food.

Whilst cooler temperatures and less food slowed the fry's growth rates and increased the time it took them to become sexually mature, irregular or infrequent water changes were still a major factor in slow growth rates in fish fry. Lack of water changes and lack of food slowed fry growth rates even more than just one factor alone.

 

[Jack TH]

Okay, that's all well and good, but that doesn't conclusively prove this hormone's existence. It only suggests it might be there.

Some questions:

1. What exactly is this hormone? Has it ever been identified? By what mechanism does it slow down growth?
2. Frequent water changes are known to encourage fry growth anyway, due to waste being removed and fresh water with fresh minerals is being introduced into the environment. How do you know it wasn't this causing the faster growth?
3. If in the wild, the hormone is washed away, and it can't have it's desired effect, why would fish evolve this ability? Animals don't evolve abilities that are useless.
4. How does the fish producing the hormone not slow it's own growth down? Surely if it released this hormone into the water, it would slow itself down?

You have a good experiment, but as said earlier it doesn't conclusively prove anything. This hormone is only one explanation, and until it's conclusively identified as coming from the fish themselves and it's method of slowing down growth, and how it doesn't slow down the growth of the fry producing it, the claim that fry produce hormones to stop other fry from growing is unsubstantiated, and saying it's a 100% fact is misinformation.

 

[Colin_T]

In my opinion, it's a growth inhibiting hormone but I cannot tell you what it's called because I never had it tested in a lab and I'm not a molecular biologist.

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My tanks were given a complete gravel clean when they got water changed and the new water had high levels of minerals in (300ppm GH) and sufficient KH to prevent the pH dropping in any of my tanks. My tapwater naturally had a GH below 50ppm and 0 KH. I used Aquasonic Rift Lake conditioner at a lower than recommended dose rate to get the water hardness to 300ppm. The Rift Lake conditioner is designed for fish from Africa's Rift Lakes and has high levels of calcium and magnesium in. These minerals are used by fish to develop good skeletons and healthy muscles. The amount of these minerals that would have been used by small larval fish fry is insignificant and would not have decreased significantly over a one or two week period.

The amount of fish waste removed during water changes was minimal during the first month of growth but did increase as the fish grew. However, the fish in the tank that was being water changed once every 2 weeks, only had small amounts of waste in the gravel that was removed with the water change. And this was at the end of the 3 month period. The smaller fish were still fed well but not as much food went into the tank because they weren't as big and didn't eat as much.

Small amounts of fish waste are unlikely to harm the fish or inhibit their growth but can contribute to the pH dropping. This did not occur in any of the tanks with the pH remaining stabile at 8.4. The pH was tested using Bromothymol Blue and a colour chart and numbers were confirmed several times during the experiment with a digital pH meter. Fish waste can encourage infusoria (paramecium) to grow, however this is unlikely to occur in a filtered aquarium or when regular water changes are done. Any infusoria growing in the tank would have been eaten by the fry.

Nitrates were never an issue and remained under 30ppm in all tanks during the 3 month period. In the tanks getting water changed daily or twice weekly, the nitrates stayed below 20ppm. For the first month while the fry were small the nitrates remained less than 10ppm in all tanks. Liquid test kits were used to check ammonia, nitrite & nitrate levels. It wasn't until the fry were being fed marine mix (at about 4 weeks of age) that the nitrate levels started to increase in all the tanks.

If the tanks became dirty enough and high levels of nutrients were inhibiting the growth, then diseases could be a contributing factor. None of the fish in the rearing tanks developed any diseases or showed any signs of disease. This would suggest the water changes and filtration was sufficient to minimise any microscopic organisms in the water.

I do not believe that replacing minerals or removing nutrients was a factor.

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Not all fish live in flowing water so whilst hormones produced by fry in a river will be diluted and washed away, it doesn't mean the hormones are not produced. Fish also produce stress hormones and breeding pheromones that are picked up by other fishes in the water. Why produce these if they only get washed away?

Fish have a much better sense of smell than people or even dogs, and can detect odours from long distances away. They use this to find food and potential mates. The breeding pheromones have been found in seawater and freshwater and in aquariums. There have been numerous reports of fish starting to breed after a single pr of fish spawns. There are two main reasons for this, one is pheromones released into the water, and the other is visual stimulation. The fish see other fishes breeding and produce eggs and sperm at the same time so there is more chance of the eggs being fertilised and less chance of their eggs being eaten. Hormones are also used to encourage some species of aquaculture fish to breed.

In a pond or lake, the water is not flowing anywhere and hormones will not be washed away. And in the ocean the plankton stay near the surface and even tho there is swell and currents moving the water around, the fry are not battered about that much because you can have calm areas amongst the moving water. If you are in the water at the beach standing in calm water and you pee in the water, it takes a few minutes for the water temperature to cool down. The same thing with fish releasing hormones. In most areas where fry occur, the water doesn't flow that rapidly and hormones can remain around the fish for some time.

Most freshwater fish fry live among plants that reduce the flow of water and hormones could be used to slow the growth of nearby fry that are competing directly with you for food.

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Hormones produced by an individual might actually slow that individual's growth. However, it is unlikely that would happen because all animals and plants produce hormones and if they inhibited or harmed the organism producing it, that would defeat the purpose of producing it.

Most hormones are produced for a reason, possibly to attract a mate, tell others there is something wrong or danger is approaching, or to repel intruders (plants use this a lot).

Whilst there may not be information readily available on growth inhibiting hormones produced by fish, it is my opinion that they do exist and occur in aquariums, and these hinder the growth of fish fry.

Without research into this area by a specialised biologist, it might never be substantiated. It's not really high on the list of something people really care about and it could be a while before someone with an interest in fish keeping and who has the knowledge and tools to play with chemicals at a molecular level, ever looks into this subject. I could be wrong and there might not be growth inhibiting hormones released by fish fry. If there is an upcoming biologist that studies this subject and proves me wrong, then I will change my opinion.

I can't see farts but I know they occur. I can't see the wind but I see what it does. Your point that is has not been 100% conclusively proven is acceptable. However, I am a believer

 

[Jack TH]

Hormones produced by an individual might actually slow that individual's growth. However, it is unlikely that would happen because all animals and plants produce hormones and if they inhibited or harmed the organism producing it, that would defeat the purpose of producing it.

In which case, that supports my point. The laws of physics don't allow these fry to not be affected by their own hormones unless they have a biological mechanism that stops it from happening.

Most hormones are produced for a reason, possibly to attract a mate, tell others there is something wrong or danger is approaching, or to repel intruders (plants use this a lot).

Exactly, which is why I'm saying this 'growth inhibiting hormone' isn't a thing.

it is my opinion that they do exist and occur in aquariums, and these hinder the growth of fish fry.

Okay, so we've got to the point of opinions. Opinions really don't matter in science, what matters is if you can prove that it's there.

I could be wrong and there might not be growth inhibiting hormones released by fish fry.

Okay, so this is a perfectly reasonable stance. What I don't understand is why you tell other people that these fish do produce hormones like it's common knowledge, when you admit yourself that you don't know if it's true?

I can't see farts but I know they occur.

You can't see them, but you can hear them, and smell them sometimes. We now know that it's part of the biological process of removing waste. Therefore, it's conclusively proven that flatulence exists. It's not really the same thing.

However, I am a believer

Belief has no place in science. What matters is the evidence that something exists. It doesn't matter what you believe.

This situation is kind of similar to Planet Nine. We've seen things that point to it being there, but it's not proven as we've never seen it and there are other explanations, which means it might not exist. What you're doing is telling people that Planet Nine 100% exists, we've seen it, and it's effects are proven science. None of that is true, and we also have evidence that points to it not existing, as well as alternative explanations for it's perceived effects. There's no reason to believe that either Planet Nine or growth-inhibiting hormones from fry are real because we don't have conclusive evidence at all, just theoretical evidence.

Although that's the part when these two things aren't so similar. Another reason I don't believe these hormones are real is because everyone has a different idea of what they are. Some say that adults produce it to stop fry from growing, others say that it's fry that produce it, etc.. Just like with religion, when there are so many different interpretations of what something is, all claiming to be 100% fact, chances are none of them are right.

The thing is, is that this happens in pretty much every field of science. Take astronomy for example. Every time something new is discovered in the outer Solar System, a scientist or group of scientists propose that it's because of a planet out there that we can't see. We now know that none of these proposed planets exists, and Planet Nine probably doesn't. Can you see how this situation is pretty much the exact same as that?

Anyway, thanks for replying calmly and rationally, a lot of people on other sites like Fishlore can't take criticism, the slightest hint that you disagree with them sets them off, and they start accusing you of everything you can think of. Massive egos and superiority complexes over there.

 

[Colin_T]

Anyway, thanks for replying calmly and rationally,...

LOL, rage rage
It's good to have differing opinions from time to time. It encourages discussion on subjects that might be ignored or disregarded.

We know animals (including fish) produce hormones and that hormones do affect the way we feel and do things in day to day activity. Something in the water inhibits the growth of fish fry and this is overcome with regular water changes. Whether it is a growth inhibiting hormone produced by the fry to help the individual grow faster or something else, we will have to wait and see. But if fry do produce a hormone to slow the growth of other fry around them, it would be an advantage to that fry.
eg: I produce hormones to slow the growth of those around me and this allows me to grow faster, and the faster I grow and the bigger I get, the less likelihood of me being eaten. There is a logical reason for it to exist.

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The whole purpose of breeding is to reproduce the species so if adult fishes produced growth inhibiting hormones it would disadvantage their own offspring and that would be contradictive to producing healthy young. I do not believe adult fish produce any growth inhibiting hormones at all.

Many of the people that have claimed adult fish produce growth inhibiting hormones keep cichlids, and I believe the fry are not being fed as well as they could be and that insufficient water changes are being done on the rearing tanks. There's also a probability there are stress hormones produced by the fry if there are other big fishes in the tank with them. Stress hormones do exist and are well documented and these can inhibit growth in fish and animals. I do not believe stress hormones were a factor in my experiments because there were no big fish near the rearing tanks, the adult fish were kept in different rooms.

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I use to tell people there were bacteria in the filter that kept water clean. That was considered crazy talk back in the 70s but now it's common belief and has been proven by scientists as fact. I also tell people we are hotels and high rise apartments for bacteria, yeast, viruses & fungus that we have a symbiotic relationship with. I still get called nuts about that

My experiments and experience over the years tells me that fish fry produce something that inhibits the growth of other fry around them. There is circumstantial evidence to suggest it does and physical evidence that water changes help improve growth rates and these results can be replicated by others. I have ruled out other factors that inhibit growth and am left with growth inhibiting hormones or another unknown factor.

I believe in the near future, there will be more research into this area and my views will be confirmed. Until then, I offer my opinion and suggestions to others and if they want to use them that is fine. If they don't want to use them that is also fine.