How big would my Iridecent Sharks get?

[Red Belly Pacu]

I have four of them. They are about 4 inches now. How big will they get? Anyway, someone told me that they will only get about 11 inches in an aquarium. That person has theirs for about 8 years.

[Silurus]

I suppose how big they get depends on how you treat them. You could probably stunt them by keeping them in a smaller tank and not changing the water frequently (if at all), but that would not be a humane thing to do, would it?

[Ron]

Maybe these will give you an idea:



I think that you have a problem on your hands.

[Red Belly Pacu]

Maybe these will give you an idea:



I think that you have a problem on your hands.

They grow that size in the wild. In an aquarium, they get smaller. Mine is only 4 inches now.

[Rusty]

They grow that size in the wild. In an aquarium, they get smaller. Mine is only 4 inches now.

Do fish magically change when you put them in an aquarium so that they do not get any bigger than 11 inches? Given proper care, fish should get larger in captive care than in the wild, due to a constant food supply, lack of predation, etc.

Rusty

[magnum4]

They grow that size in the wild. In an aquarium, they get smaller. Mine is only 4 inches now.

The to pictures shown are small specimens compared to the adult size. However they may never reach anywere near this size in aquaria, and how fast they grow depends on your feeding, tank size, water changes.. ect. The reason why you very rarely see large Iridecent Sharks on display is because out of the many thousands imported each year all live a comparativly short life.

[Red Belly Pacu]

I do not think fishes grow bigger in an aquarium than in the wild. Fishes can eat more stuff in the wild. Here is a person who wrote that her Iridecent grew from 8cm to only 33 cm. She had it for 11 years. Keeping a fish alive for 11 years, she is doing something right. Here is her post about her Iridecent Shark:

"What a great fish to have. I got my "baby" when she was just one of the little ones in the pet store, 11 years ago. From 8 cm to her current 33 cm, she has given us nothing but pleasure. She is always the first thing someone notices when they come to my home. Plus, she is a very hardy fish. Through divorce, marriage, and several moves in between, she has adjusted fine every time. One last move planned, and that´s to a new 850 liter home very soon. "

[Red Belly Pacu]

Here is another owner. He said this about his Iridecent:

"I have 5 Irridescent Sharks. I did not know they would get so big. One is 16 years old and 45 cm long. The other 4 are at least 5+ years old, 3 are 45 cm long, and the small one is about 15 cm long. They were all about 7 cm long when we first got them. They are in an 350 liter tank. The addition of a DIATOM filter seems to take care of disease problems for them. I use the added filtration every 2 or 3 weeks."

[magnum4]

Red Belly Pacu I am not sure what you are trying to prove with your posts, yes there size is stunted in an aquarium, however i and others are trying to warn you that they have got a extreemly large maximum size. Do you think it is fair that a fish with the potential to grow to 6ft should be forced to live in an aquarium normally smaller than its own adult size?

[general-sherman]

fish DO NOT grow to the size of the tank, this is an utterly stupid misconception. they only get STUNTED, which is not humane and shortens their life span.
if you want to keep pangasius sp. in captivity, buy a public aquarium. preferably one on the large side. anything else is the equivilent of keeping a large breed of dog in a 4'x4'x4' cage for life. its cruel and unusual punishment and should not be inflicted on animals. they don't deserve it and have no way to tell us how uncomfortable they are. its up to us to treat them with respect.
when you see a big fish in a small tank, or a puppy in a cage, or an elephant chained up at the circus, or bears chained up, or alligators in tiny concrete ponds...what does it say about human beings?

[Jools]

I do not think fishes grow bigger in an aquarium than in the wild. Fishes can eat more stuff in the wild.:

No, not true. Fishes have to find food in the wild and are prone to the vagarities of season, weather etc etc etc. They should not have to do this in captivity. Mbuna are a very good example which has been explored scientifically I think.

This is pushing the arugument, but how about you lock one person up in a supermarket for 6 months and drop one person in a tropical rainforest - who will end up with more food in that time? Or even use this argument to explore quality of food.

Here is a person who wrote that her Iridecent grew from 8cm to only 33 cm. She had it for 11 years. Keeping a fish alive for 11 years, she is doing something right.

No, this is a testiment to the hardyness of the fish. If fish are truly happy they will reproduce; I don't see that happening.

Irrespective of whether you choose to stunt your fish or not, these are shoaling fish. Even to keep a shoal of stunted (circa 20") individuals you would require a huge tank.

I ask you this, If it didn't look like a true shark, would you be so keen to keep it?

Jools

[Red Belly Pacu]

fish DO NOT grow to the size of the tank, this is an utterly stupid misconception. they only get STUNTED, which is not humane and shortens their life span.
if you want to keep pangasius sp. in captivity, buy a public aquarium. preferably one on the large side. anything else is the equivilent of keeping a large breed of dog in a 4'x4'x4' cage for life. its cruel and unusual punishment and should not be inflicted on animals. they don't deserve it and have no way to tell us how uncomfortable they are. its up to us to treat them with respect.
when you see a big fish in a small tank, or a puppy in a cage, or an elephant chained up at the circus, or bears chained up, or alligators in tiny concrete ponds...what does it say about human beings?

Most fishes regardless of what they are grow smaller in an aquarium than in the wild. Also these people that I mentioned had their Iridecents for quite some time. They did not seem to have a short life span and they were doing something right. Also many people like to have big fishes in their aquariums. They do not want just guppies or small tetras in an aquarium.

[Jools]

Most fishes regardless of what they are grow smaller in an aquarium than in the wild.

How do you know this? Of all the fish I can think of that I have collected in the wild I have seen them larger in captivity. The point I think is that if they DONT get larger in captivity then we are doing something wrong.

Also these people that I mentioned had their Iridecents for quite some time. They did not seem to have a short life span and they were doing something right.

How do you kinow this, I mean for you to state they do not have a short life span would imply you could tell me how long they should live for? What if they live for 50 years in the wild for example?

As to people wanting to keep big fish, yeah, that's great but there are some really cool ones that do not grow this big, are not nervous shoaling fish and might even look a little bit like sharks.

Jools

[magnum4]

Red belly pacu, you have been given an answer to your question and now you are argueing with no evidence to match your statements. If you are waiting for someone to give you the answer that YOU want to here then you will be waiting for a long time. we are not going to tell you "yes its fine buy as many sharks as you want put them in a small tank and they will live a long happy life".

[general-sherman]

red belly pacu, i think you'll find this is a site that actually CARES about fish. this site is not populated by idiots who congratulate themselves on their "skill" as a fishkeeper by being able to cram giant species of fish into modest sized tanks. if you want to talk to people who have pangasius, redtails, tiger shovelnose, pacu, arapaima and many, many other species that should not be in the aquarium trade, theres plenty of other sites out there.

[Red Belly Pacu]

Most fishes regardless of what they are grow smaller in an aquarium than in the wild.

How do you know this? Of all the fish I can think of that I have collected in the wild I have seen them larger in captivity. The point I think is that if they DONT get larger in captivity then we are doing something wrong.

Also these people that I mentioned had their Iridecents for quite some time. They did not seem to have a short life span and they were doing something right.

How do you kinow this, I mean for you to state they do not have a short life span would imply you could tell me how long they should live for? What if they live for 50 years in the wild for example?

As to people wanting to keep big fish, yeah, that's great but there are some really cool ones that do not grow this big, are not nervous shoaling fish and might even look a little bit like sharks.

Jools

I have a lot of tropical fish books. Most notable fish authors such as Dr. Herbert Axelrod who is the founder of Tropical Fish Hobbiest magazine and many of his books he wrote stated that fishes usually grow smaller in an aquarium than in the wild.

Keeping a fish alive longer than 5 years is a long time in my opinion. It might not be for you but the fish keepers who are doing this is doing something right.

[Red Belly Pacu]

Also I go to a piranha messege board frequently. Most of the people over there would want a 15+ inch Black Piranha. They can get to 24 inches in the wild. People can usually buy the Black Piranha when small and they know that the chances are slim that the Black Piranha would grow to 15+ inches in an aquarium.

[magnum4]

I have a lot of tropical fish books. Most notable fish authors such as Dr. Herbert Axelrod who is the founder of Tropical Fish Hobbiest magazine and many of his books he wrote stated that fishes usually grow smaller in an aquarium than in the wild.

For the record this is early work, well out of date.

I was going to write more, but i stopped myself i have realised that we are all just wasting our time, you just wont ever get it!

[Ron]

Keeping a fish alive longer than 5 years is a long time in my opinion. It might not be for you but the fish keepers who are doing this is doing something right.

IMO, that is an incredibly generalized statement and therefor incredibly worthless. If you kept a neon tetra alive for 5 years I would give you tons of credit, but if you thought it was an accomplishment to keep a pleco or syno over 5 years I wouldn't be that impressed because they should live much longer than 5 years.

I don't know much about piranha, but I have a feeling that the fish you are speaking of are not being kept in proper conditions and therefore not reaching 24" or whatever you stated. For starters, what size was the tank?

[Red Belly Pacu]

I have a lot of tropical fish books. Most notable fish authors such as Dr. Herbert Axelrod who is the founder of Tropical Fish Hobbiest magazine and many of his books he wrote stated that fishes usually grow smaller in an aquarium than in the wild.

For the record this is early work, well out of date.

I was going to write more, but i stopped myself i have realised that we are all just wasting our time, you just wont ever get it!

Well the scientific name for the Cardinal Tetra, Paracheirodon axelrodi is named after Dr. Herbert Axelrod because he discovered the fish. Also many other fishes in their scientific name is named after him.

I would trust Axelrod more than you. Here you go slamming the founder of Tropical Fish Hobbiest Magazine and an author of many tropical fish books. I can tell you do not read a lot. Dr. Axelrod is a scienctist and his fish is his speciality!

[Jools]

I have a lot of tropical fish books. Most notable fish authors such as Dr. Herbert Axelrod who is the founder of Tropical Fish Hobbiest magazine and many of his books he wrote stated that fishes usually grow smaller in an aquarium than in the wild.

I just counted and I have 27 books by Axelrod or co-authored, lots more from TFH. In one particular section from his Encylopedia (first edition) he describes and angelfish the size of a dinner plate kept by a Florida Fish farmer.

I also have a book by him stating that discus are very difficult to keep and breeding is near impossible. Now, by your argument, this must be true right?

Now, can you quote me which book you refer to and a page for the statements you make. I will probably have the book here and I can copy up the text so we can debate the point?

How about you think outside the books and forums you read...

Jools

[Jools]

Also I go to a piranha messege board frequently. Most of the people over there would want a 15+ inch Black Piranha. They can get to 24 inches in the wild. People can usually buy the Black Piranha when small and they know that the chances are slim that the Black Piranha would grow to 15+ inches in an aquarium.

What's your point? If there are other idiots in the world then it's OK to be an idiot too? I refer back to my point on reproduction. How many people are breeding these fish...

Jools

[general-sherman]

red belly pacu tell me which book dr. alexrod talks about HIS OWN personal experiences in keeping iridescent sharks. where does he say: "i have kept this fish, and sure, they grow big in the wild, but the one i had never did. i kept him for years in a 4ft tank and there was never a problem."
or does he just give a general overview of the fish? dr. axelrod is highly respected in aquarium circles, but many of his books are now VERY out of date. many of his books were in fact written before scientists and aquarists realised that if a fish doesn't grow to its maximum size and reach a maximum lifespan in captivity then we're doing something wrong. and if we follow this plain logic through we should see that there are hundreds of fish species that should NEVER be kept in the average size aquarium (meaning anything that can't fit in an AVERAGE SIZE HOME). this is not an opinion, it is the way things are.

[magnum4]

Everone TFH books by Dr. herbert R Axelrod ready. "Jumbo fishers for the large aquarium" I felt this book would be the most approprite for this post.

Page 135 concerning oscars, quote "the largest specimens I have ever seen were 25-30cm (10-12 inches). I never saw very large specimens in the wild, so they probably grow larger in the aquarium".

Page 298 Metrodontotus tigrinus, quote" the catfish grew and grew and grew untill they outgrew the tank after swallowing everything else in it".

page 343 Arapaima gigas(red belly guess how big this grows?) quote "They cannot be recommended for any aquarium less than 200 gallons"

Red belly did you learn anything from this?

[00 MooRRii 00]

We could all sit here and tell Red Belly Pacu that he is wrong but by the looks of things he just doesn't want to listen, so why bother. I spend half my time on the internet trying to inform people on how to best keep their fish, what water perameters and size etc. Most listen and try do the best they can, but then you get the people like this guy who just doesn't want to listen.

Red belly pacu- You bring up a semi-valid point about the infamous Black pacu. The reason you see aquarists who want such large ones is NOT because they do not atain their full adults size in aquaria but because they are extremely slow gowers, said to only grow 1" a year or less in adulthood. So the reason they are plucking so many out of the wild is because how many people do you know that are going to spend 20years raising a pirahna to it's full potential then sell it?

[Katman]

From what I see you are talking about apples and oranges.
From what I have found fish on the lower end of the food chain tend to have a shorter
life span .They mature fast and breed befor they become lunch. Believe it or not
size is a handycap to a fish after they reach a certain size. They start losing their
ability to swim and maneuver due to added weight and body shape. Therefor they become lunch. So it is logical that this type fish will grow bigger in a protected
environment.
As for the top of the food chain goes. I have found that fish in the wild tend to get
bigger. Most of the larger cat fish take years to get to sexually mature 4 to 7 years.
Most people fail to keep there fish alive that long,Or have the space to accomidate
the groth of the fish. All this aside I have never seen a preditor cat fish get bigger
in captivity than the wild.
While we are on the subject of fish size .I notice that most fish size is based on the
largest caught or record size. I would think this would keep a lot of people from
keeping fish that are not going to get as big as they think they could get.
I have been chasing records all my life ,and belive me they do not come easy, if at all.
To tell some one that a fish could get 10 feet long when the average is three foot,
is like telling you to put 10 foot ceilings in your house because your kids could grow
to 9 foot tall. It is possible but the chances are slim.
From what I have gathered on farm raised Pangasius ( this was back in the 60s)
six pounds in 12 mounths was average. These were not reailly farm raised as they were
in a fenced off lagoon on a main river. I have not seen this done ever on the fish farms.
To say what is large or normal or average for one area is not true for another, so any one who says something for a FACT should be careful.

[nolan]

i have kept these fish and they do indeed get large they can attain large sizes in captivity mine grew to around 16+" and they lived in a large holding vat rather than a tank. they will crash around in a tank and injure themselves they are real pigs when they eat as well and a good filtration system in essential. they grow quite quickly, my albino one was the largest and unfortunatley decided to jump out of the vat when i was cleaning it out and later died from the stress. having kept several large catfish over the years including a wells cat which is still around living in one of my friends ponds and has now reached thirty inches or so last time i was there. i would say that the more space they have and the amount of food they eat as well as the enviroment they live is the main factor when i comes to how big they grow.
generaly in my experience fish kept in ponds grow larger than tank kept fish. probably due to a constant food supply and more water volume.
although these days i just keep synos and other small size cats they are just as entertaing as the large ones and a lot cheaper to keep!!
just my opinion

[rfb]

I have two sharks in my 125 gallon aquarium and they seem very content with things.
There from what i read some people that were displacing human emotions on this suject and to a degree this is ok but going to the point that some did was strange.I thought the entire time that
I was reading some the phrase couch doctor came to mind.It is time to realise that we are the humans and must do at the time what we think correct for us and if you like a fish get the fish enjoy it, love it and enjoy the splendor of the fact that you are doing something for you and
your weelbeing and then IF by chance the fish is a problem DEAL with it do not displace emotions
enjoy the sheer beauty of this wonderful hobby.

[magnum4]

It is time to realise that we are the humans and must do at the time what we think correct for us

says it all!

whats the problem with enjoying the hobby with species that don't grow massive?

i'm sick of having the same argument all the time. The views expressed above are from experience people who spend alot of time trying to help beginners, the advise is as always take it or leave.

[general-sherman]

I have two sharks in my 125 gallon aquarium and they seem very content with things.
There from what i read some people that were displacing human emotions on this suject and to a degree this is ok but going to the point that some did was strange.I thought the entire time that
I was reading some the phrase couch doctor came to mind.It is time to realise that we are the humans and must do at the time what we think correct for us and if you like a fish get the fish enjoy it, love it and enjoy the splendor of the fact that you are doing something for you and
your weelbeing and then IF by chance the fish is a problem DEAL with it do not displace emotions
enjoy the sheer beauty of this wonderful hobby.

I suppose you're above human emotions are you? I emphatically disagree with the above post. Are you suggesting that we humans can indulge in animal cruelty just because we want to? Just because it might make us feel good?
I, on the other hand, do "displace my (pathetic) human emotions" when I lower myself to think about fish locked in innapropriate size housing. After millions of years of evolution...some people still have some evolving to do...Or prehaps they missed out on some crucial developement proccess as a child? Did you start torturing animals at an early age rfb?

Idiot.