Different sizes

[nimbusv]

Is it OK to mix small discus with some bigger? lets say put 1 4" with 5 2"??

[M0oN]

shouldn't be a problem so long as you aren't mixing a lot of large discus with only a few small discus

[nimbusv]

OK MOoN, thanks a lot!

[discus_nw]

I wouldn't.

[nimbusv]

I wouldn't.


Why is that???

[1977]

It is not proven scientifically as far as I know but word is that discus that grow faster or larger discus can release a hormone that will slow growth on the other fish. Also the larger or faster growing discus could be males and will be more aggressive and might discourage the other discus from eating as freeley. I follow the policy of placing different sizes seperately.This is what Iv'e been taught by some very respected breeders.

[discus_nw]

1977's answer is similar to the line of thinking I subscribe to.

[M0oN]

Blah, bunch of rubbish, I keep 10 juvenille's with 2 full grown discus and they've been gaining over an inch a month...

Just make sure they all get their share of food, even if they did release hormones daily water changes would counter any ill effects...

[Bou]

I have to agree with MOon on this one.

If hormones were indeed an important inhibiting growth, then in order to fully grow discus, one would need to do 100% w/c daily! IMO, you should concentrate on the quality of water and regular and frequent feeding schedules which would allow every fish to have their fair share of the food!

HTH,
Bou

[yonghui]

diff size small will have less food to eat.

[aqua]

I have 4 discus@1.5", 5 @3", 5@4" and 4 @5.5 to 6" in a 100 gallons tank
and it seems they get along well. The little ones always get to the food source first. Lucky for me, I have no bully in my tank! :-)

[lsuber]

I have a very similar situation to aqua. One of my smallest fish always makes it to the feast first, and isn't shy about taking his/her share. There are two other smaller ones in the tank that have never eaten all that great, regardless of tankmates.

[discus_nw]

Moon,

And just how do suppose a daily water change would elimenate GIT in a closed system, countering any ill effects? (Wattley calls it a toxin rather than a hormone. If it does exist, it most likely is a protein, so from that, it might suggest to us it is a hormone) :)

[mattrox]

People keep metioning hormones that adult discus release which inhibit growth.
Would someone please point me to a scientific artical that 1) states that they release G.I.H. into the water and 2) that names the hormone(s) concerned? I would like to learn more.

Unless it is just a speculation???

[lsuber]

I'm a bit skeptical as well. It seems to me that in the wild this would be detrimental to the species. If the young aren't able to grow and mature to produce offspring, seems like it threatens the survival of the species.

[DarkDiscus]

The theory is that in the wild the toxin is diluted so quickly due to the huge volume of the amazon river that it does not affect the fish or does so only in a very limited fashion.

And yes, it is just a theory - there is no proof as far as I have ever seen.

John

[discus_nw]

Yes, Wattley speculated that such a toxin may exist. He called it a toxin and not a hormone. He has mentioned this toxin in several of his column responses. However, as I stated previously, if it does exist, it is most likely a protein. If that is true, then most likely the protein is a hormone of some type.

I have observed growth rates in males in my tanks. What I have seen is what I base my opinion of raising different aged discus together. Whether it be GIT or competition for food, something causes a growth difference. There were some interesting results when the larger male was removed.

For some reason, I have not noticed any problems regarding the females.

In a closed system, the volume of water needed to minimize exposure to GIT (if it exists) would not be possible for the average hobbyist/breeder.

[Scrappi_tt]

Some People would say yes and some would say no....

It works by trial and error. Try it first and if you the bigger ones picking on the smaller ones then seperate them....

[1977]

I don't think this would inhibit reproduction or maturity, just growth rate and maximum size. Either way I think it looks better to have similar size fish together.

[Asian Discus]

This is certainly a highly debatable topic. Let me offer a view from an Asian breeder's perspective...

There is no conclusive evidence to prove that 'GIH' does or does not exist. Most of what we hear is based on anecdotal evidence. When it comes to discus raising, there are many methods to achieve the same goal... which is good growth. But for the sake of what i'm about to bring across, let's assume that 'GIH' does exist.

Keeping two adults with 10 juveniles might not have as much consequence if you have a tank with a larger volume of water. However, the results might be different if you are keeping the same number of fish in a smaller tank. But even if you are using a smaller tank to house these 12 discus, daily water changes of 100 or even 200% can maintain lower levels of 'GIH'. These massive water changes would certainly whet the appetite of the juvenile fish as the water is always kept clean (I refer to a bare tank).

Such theoretical applications might not sound practical for a planted tank or even in a country that has changes in seasons. But for asian countries like Singapore and Malaysia, such massive water changes are widely practiced and have wrought positive results in bare tank raising. Feeding patterns and water quality play a big part in the eventual growth of a juvenile discus. Ultimately, each hobbyist needs to evaluate what he hopes to achieve from the hobby as this would dictate his/her emergent behaviour towards the hobby.

Suffice to say, it would be overly simplistic to assume that it is advantageous to keep large discus away from juveniles. This statement would also apply to the reverse assumption that it is alright to keep them together. Rather, it would be prudent to consider the myriad of aspects that factor into raising juvenile discus. Let's think of each discus as an individual with a distinct personality. Given the unique conditions in different breeders' homes, there might be results that defer from the acceptable 'norm'. This is not entirely impossible.

It is not my intention to offend any parties with my views and I hope this offers a dissimilar facet to an age old debate. :)

[Willie]

All the hormones that are produced by fish are well characterized. There is no such "growth inhibiting hormone". Jack Wattley is now careful to say that this is a "growth inhibiting substance" and definitely not a hormone. Logic would tell you that it is not a protein, as free proteins could not survive in an ecosystem. So, there is supposedly a mysterious substance that inhibit growth in the smaller fish.

Note that in the world of fish biology, there is no other examples of similar "non-hormone" substances. Some plants, e.g. oak trees, will produce phytoalexins that can inhibit surrounding growth. But there is no documentation of such mechanisms in fish. A big difference between the two is that plants cannot swim away from phytoalexins.

What could such a "substance" be? Well, it could a mysterious molecule that no one knows about. But that's really just hand waving. All such comments are purely speculative and provide no clear direction.

On the other hand, it could be something quite simple, like nitrate. Big fish may produce more nitrate. Smaller fish could be more sensitive to nitrate than bigger fish. Certainly smaller fish need better conditions to grow. In every animal species, conditions at early stages of development have far greater impact than conditions at adulthood. For example, children who underwent starvation can be physically and mentally stunted. The best conditions at adulthood would not reverse the damage.

If it is nitrate or another waste product, e.g. urea, then large large water changes would take care of the problem. (Urea is speculative. I don't know if fish produce urea.) Of course, very few non-professionals maintain large, frequent water changes over the life of the fish. This includes your birthday, your kids' birthday, Christmas, wedding anniversary, etc. ;)

Willie

[mattrox]

My understanding is that fresh water fish don't produce urea as a waste product. They need to get rid of large amounts of dilute urine to maintain their water balance. Ammonia requires large amount of water to dissolve compared with urea. It would be an energy cos to the fish to turn ammonia into urea and is unneccesary due to the amount of water they expel.

Does this sound right to the Ichthologists?

[mattrox]

I just looked up my Animal Physiology book. Fresh water fish have urea as 10% of their nitrogenous waste.

[discus_nw]

Wattley never said it was a hormone. Everthing I have read that JW wrote states the word "toxin". But, to suggest that suggesting the "substance" is a protein is illogical, is itself illogical.

There are 5 structural classes of hormones:

1) Proteins
2) Glycoproteins
3) Peptides
4) amino acid derivitives
5) steroids

These proteins then have 6 basic functions:

1) Homeostasis
2) Regulate growth and developement
3) Promote sexual maturation and facilitate the
reproductive process.
4) Regulate energy production and stabilize metabolic
rate.
5) Help the body adjust to stressful or emergency
situations.
6) Regulate other hormones (promote or inhibit production of)

Growth hormone (GH) is a protein. So, if GIT is indeed being produced by discus, and if it is a hormone, it would follow that it would have to be a protein or steroid. If one has ever witnessed mass spawning in a community tank after one pair has spawned, they know that hormones can and do trigger certain behavior in discus.

There are many causes of discus not growing properly, nitrates being one. But, we are not talking about all reasons, just the possibility of "GIT" existing. This rules out nitrates as a subject in this thread. To my knowledge, nitrates are not produced by discus. Rather, they are metabolic by-products of bacteria.

Urea is the nitrogenous end product of protein catabolism in mammals. Not all animals produce urea. Birds and lizards produce uric acid as an end product. For bony fish, the chief product is ammonia. This would tend to rule out urea as a cause.

Some amphibians are suspected of also producing a type of "GIT". Again, JW noted similar events occurring in his Dart Frogs while they were in the tadpole stage that he noted in his discus tanks.

No one knows if GIT exists, or if it does - what it may be. All at this point would be speculation and strictly a topic for discussion. No one can say with certainty that it exists. Or, that it doesn't.

Scientists are just now finding chemicals being produced in the human body and their functions. How can one believe that the chemical processes in fish have been researched to a higher degree? :)