Platies never grow as large as sold at the store

I am not sure if it is just my experience or a common problem, but for some reason platy fry born in my tank never seems to grow to a full size, like the size commonly sold in pet stores. Just curious as to what could be the reason.

To be fair, I do not separate the fry, so it is not fed any extra than my other fish in the tank (which is usually once a day; sometimes, every second day). Most fry always gets eaten, and only few would survive into adulthood. And those who do survive into adulthood, never really grow larger than what one would expect a junior platy fish look like (about 1/3 of the size of platies sold at pet stores). I wonder what might be the reason. My current tank (18 months old) is an understocked, heavily planted 40 gallon breeder. No heater: about 75 F during winter time and 85-85 F in the summer (I am currently in Arizona, so summers are hot). My previous tank was 29 gallon (also heavily planted), and it was in a different state, so I used a heater to keep the tank consistently around 79-82 F. It has been the same experience with both tanks for me: platies born in my tanks never quite grow to adult size, stay the size of juniors (~1/3 of store bought platies).

I feed my fish Hikari frozen bloodworms and two types of flakes (New Life Spectrum Optimum Flakes and Sera Natural Flakes).

Photo of my 40 gallon for attention.

 

...so it is not fed any extra than my other fish in the tank (which is usually once a day; sometimes, every second day).

I would guess, if you fed your fry more (and more often), they would grow faster and to a bigger size.

 

I would guess, if you fed your fry more (and more often), they would grow faster and to a bigger size.

Thank you! It really isn't a matter of growing faster or slower (it wouldn't be a problem if they simply just grew slower), the problem is that their fully-grow size is about 1/3 of parents' (and typical platy sold at pet stores).

 

It maybe that if they don't have a lot of food when they are young, it inhibits their growth.

 

Any pics of the fries?

 

Any pics of the fries?

I gave away all but one recently, this tuxedo platy is probably close to 6 months old. Some that I gave away were over 1 year old, but they just appear to stay at that size. Pretty much all of the youngsters that I had stay about this size.

 

Hmm are you certain it is stunted? The pet store platies would have had the same timeframe to grow even bigger than when you purchased them.

This juvenile might be the same size as the others when first purchased. In my experience most platies in LFS are not full adult sized... If you measure this juvenile and compare at the LFS then that might give the definitive answer

 

Hmm are you certain it is stunted? The pet store platies would have had the same timeframe to grow even bigger than when you purchased them.

This juvenile might be the same size as the others when first purchased. In my experience most platies in LFS are not full adult sized... If you measure this juvenile and compare at the LFS then that might give the definitive answer

The juvenile was born in my tank. It's about 6 months old. However, I gave away several platies born in my tank, some over 1 yo and all a similar (smaller) size. I started to wonder whether breeders might be feeding platies some sort of growth hormones to make them grow this big?? That's why I decided to ask if other hobbyists might have had a similar experience of smaller platies when born in their care.

 

But the parents would have also had 1 year to grow? Thats why i wanted to compare to the store rather than to the parents

Also aggression and community hierarchy can cause some fishes to remain smaller

 

I noticed they grow bigger in a bigger aquarium. The ones farmed come from ponds I think.

 

I think it's not feeding enough. If you feed an animal half of what it needs when it's growing, it's not that they take longer to get big, they just don't get as big cause they didn't get enough to eat during their youth.

 

When I let fry grow out in a community tank they often don't reach their parent's size. I just can't feed them enough without polluting the tank and over feeding the other fish. In a grow out tank, I can feed several times a day and stay on top of of water quality while they grow faster and larger than in the community tank.

 

Feeding is exactly the difference. The farms are using intensive feeding and water changing schedules to put on mass quickly, which translates to growth.
If they have everything they need at all times, and pristine water, they can reach their maximum potential, generally home breeders don't work this hard on growing their fry so the adult sizes are smaller.

And yeah, that's the purpose of the grow out tanks, control. Adults being heavily fed get fat, juveniles gain mass and grow until they reach their maximum, and the easier you make cleaning on the grow out tank, the quicker it is to do it and maintain that top water quality no matter how much food you're giving them that goes to waste, but once you have it dialed in and set for frequent small feedings, there's not a lot going uneaten, but there's still a ton of poop that needs to be removed.

 

I noticed they grow bigger in a bigger aquarium. The ones farmed come from ponds I think.

I noticed they grow bigger in a bigger aquarium. The ones farmed come from ponds I think.

Thank you! I did think of that as one of the possible factors as well. My tank is 40 gal right now, and before that, it was 29 gal. Plus, heavily planted, so the thick substrate probably takes a good 10 gal of water out of it.

But the parents would have also had 1 year to grow? Thats why i wanted to compare to the store rather than to the parents

Also aggression and community hierarchy can cause some fishes to remain smaller

No aggression in the tank. Bad-tempered platy fish / fry is always rehomed at the first notice of aggression.

I think it's not feeding enough. If you feed an animal half of what it needs when it's growing, it's not that they take longer to get big, they just don't get as big cause they didn't get enough to eat during their youth.

Feeding is exactly the difference. The farms are using intensive feeding and water changing schedules to put on mass quickly, which translates to growth.
If they have everything they need at all times, and pristine water, they can reach their maximum potential, generally home breeders don't work this hard on growing their fry so the adult sizes are smaller.

And yeah, that's the purpose of the grow out tanks, control. Adults being heavily fed get fat, juveniles gain mass and grow until they reach their maximum, and the easier you make cleaning on the grow out tank, the quicker it is to do it and maintain that top water quality no matter how much food you're giving them that goes to waste, but once you have it dialed in and set for frequent small feedings, there's not a lot going uneaten, but there's still a ton of poop that needs to be removed.

Thank you so much! Makes total sense! I am glad to hear that it's not just me who has fry smaller size in a community tank. And yes, can't overfeed the adults and trash the water in the main tank (I work 7 days a week, so can't do frequent water changes). Before this moment, I did not really care if fry grows or not because whatever fry doesn't get eaten, I'd just simply rehome (as platy youngsters can be quite the ***holes to one another, I dislike to see their nasty dynamics, and just usually rehome). But a few that I wanted to keep, stayed small, so I'd eventually just get annoyed and rehome them, too.

But right now, I have just finally found imported hifin sunset platies at a local fish store. So, because of how difficult it was to find those (I looked for 18 months, since I started this 40 gal tank), I am hoping to raise some of their fry to normal size, so that I have several generations of my own hifin sunsets. They are still in 10 gal QT, and are going to stay there for another 2 months at least (as they did come with health issues that I am working on right now (posted on this forum about that), and then I will be doing a few rounds of deworming with PraziPro and FRITZ Expel-P before they ever get to be transferred to the main tank). So, maybe if any of the females has fry in the 10 gallon QT tank, it would be easy to net it out. In the 40 gal, it is almost impossible to net the fry out as they hide in dense vegetation until they get eaten, at one point or another. I do have also have a 3-months old, 20 gal long dirtied filterless tank (inspired by Diana Walstad method, photo attached), so perhaps with frequent water changes while the fry is young, this could do the trick in the future.

I thought that platies are fully grown at 4 months (that's what google search shows). But I see comments mention one year?? Is it really the case that it takes them a year to grow to the size at pet stores? A female platy that I have right now, I bought her in September 2020 fully grown. I always assumed that she was about 4 months old at the moment of buying. But if it really takes them a year to grow out to full size, that would make her about 3.5 yo old lady??? I moved her with me from CO to AZ back in 2021, she is one of my original fish from the 29 gal, and I am not ready for her to die from old age just yet .

 

Fish grow as long as they live, but most of the growth occurs in the early stages. Getting growth on your fish is a matter of three things: food, space, and water cleanliness. Screwing up any one of the three will result in smaller fish. Your problem is competition with adult fish for the food. Space not only involves room to grow, but it also involves the competition for resources.

On some species the need for space can be partially overcome by extreme water changes. Some Discus breeders in Asia are known to do 90% water changes daily. Their feeding regime is equally extreme. They get maximum growth for the first three months, at which point they are large enough to select future breeders and sell the rest. Quick turnover equals profit for them.

The late James K. Langhammer raised Swordtails to what most consider full adult size in less than 5 months by doing 70% water changes every three days. These were as large or larger than the fish you see in stores. Raised in commercial ponds, Swordtails can reach 6 inches in about a year. In the wild, they have been seen larger than this.

A lot of people think getting fish to spawn is the hard part. The real challenge is raising the fry. If you want to get full size on your platies, you need to isolate the fry ASAP and give them extra attention in care, i.e., feeding and water changes.

 

There are multiple reasons why offspring won't grow up as they should be. Quality of the food, the frequency of feeding, the temperature, the open space, the frequency of water changes, the hierarchy but also genetics can be in play.
So, one of these (or more) can affect the growth of the offspring.

 

chromedome52 thank you so much for such a detailed reply. It definitely makes sense!​

 

You didn't mention anything about waterchanges. I'm guessing you don't do alot since it's planted. While nitrates can remain low with plants, water changes are necessary to remove hormones given off by bigger fish that will stunt growth of smaller fish. Plates and most other commercial fish are given a constant supply of fresh water from wells and overflow/ runoff of old water. When I raise guppies mine get big and healthy about the same size as petsrmtor me fish. But some others people guppies end up small. They can't figure it out. What's the secret? Warerchanges

 

You didn't mention anything about waterchanges. I'm guessing you don't do alot since it's planted. While nitrates can remain low with plants, water changes are necessary to remove hormones given off by bigger fish that will stunt growth of smaller fish. Plates and most other commercial fish are given a constant supply of fresh water from wells and overflow/ runoff of old water. When I raise guppies mine get big and healthy about the same size as petsrmtor me fish. But some others people guppies end up small. They can't figure it out. What's the secret? Warerchanges

That's very good to know! Thank you so much! I never thought that water changes can affect growth, but the mechanism of hormones in the water stunting growth totally makes sense! My brain functions in term of understanding the underlying mechanisms behind things, so this is perfect! Water changes wise, I have not been very consistent. For close to a year after starting a very demanding new job (pretty much working 7 days/ week), I have completely neglected my tank for months. But I am getting way better now and trying to do weekly water changes of 15 gallons on a 40 gallon tank (in reality, is you deduct the thick substrate and wood (I have three pieces of wood in this talk even though they are hidden by plants), it is probably realistically only about 30 gallons of water. So, it is ~50% water changes weekly now. You comment has definitely motivated me to not slack off on water changes. Recently, I did manage to turn my neglected tank around, which I am pretty proud of! First photo is July 2022, second photo (same tank) from about a week ago . The tank was so neglected that val took over. I was at the point of making a choice to either rehome to talk as it was a complete disaster or to try turning it around... I am glad I went with the latter

 

Heck yeah glad I could help and shed some insight that nobody else would have mentioned.

 

I agree , for angelfish fry I’ve read it’s recommended to feed them small meals but several times per day when growing them out, so they grow faster and stronger. Although fry usually also feast on Algea and other micro things in the aquarium, good frequent feeding would also benefit them while them are growing rapidly.