Runts

[Ralph]

Are runts caused by genetics or environment, or both?

Are they doomed to their size for the rest of their lives?

I've heard that they can breed normally with normal spawn, is that true?

[EthanCote.com]

Hi Ralph,

From what I have learned on Simply, it appears environment seem to be a big factor in creating runts. I'm sure genetic has something to do with it but in most cases probably plays a much smaller role.

From reading the many posts, in everyone's tank, there appear to be a runt or two which lead me to conclude environment plays a larger role than genetic. Another example pointing toward environmental factor is there are talks of removing the runts to its own tank and it will grow up normally.

On the biological side, there are talk of a Growth Inhibiting Factor that gets released by the Discus to stunt others in the same tank thus causing runts. Obviously this is inconclusive but still there are quite a few that believe in this theory even the respected Mr. Wattley.

From my own 6 Discus in a 75 gallon tank, I got one runt. That is 1 in 6 chance of getting a runt, the number seems rather high to suggest genetic playing a huge role but then again, nothing is conclusive.

Hope that shed a bit of info to your questions.

Others here, please post how many runts you have and describe the condition the runts were created.

Thanx.


Cheers,

Chi.

[Ralph]

Hey Chi,
I got the exact same ratio as you do, two runts out of twelve.

I went through a thread on GIF and found it a little frustrating. They don't know how it works and there is nothing you can do about it. I'm getting ready to move my two to a different tank and see what happens.

My son's zebra danios had a large hatch of fries. Two months later, with normal fish tank care, and there are several adult size fish, some that didn't grow after the first week, and the rest are inbetween. But it is a huge range of growth, in fact the biggest are eating the smallest.

I'm going to see if any research has been done on nondiscus fish. Somebody must have looked into this, probably the fish hatcheries have done some research, it's big bucks for them.

[fcdiscus]

Personally I feel it is a bit of both. Since it can be genetic, I believe it is not good to breed a runt. JMO- Frank

[Keystonediscus]

well said frank I agree it is heredity as well as water conditions. there are always runts in spawns. these fish are usually culled. but even healthy fish can become runts if they are not given clean living conditions and a healthy diet

Brian Bender
Keystone Discus
www.keystonediscus.com

[Keystonediscus]

Chi and Ralph I missed your post on m first pass through. Chi I think your 75 gal tank with 6 discus is perfectly normal. its not neccessarly true that in every 6 fish one will be a runt. what you are seeing with the 1 small fish is a result of the pecking order in the system. in every tank you will always have one fish that will not grow like the rest. this is due to being out competed for food. one fish will be the boss of the tank the others will fall in line behind him. the one that gets picked on the most will end up being the smaller fish in the group. I always keep one fish that i dont quite like in each tank to take the abuse from the rest. this way the ones i want to grow out to adults will get what they need.

Brian Bender
Keystone Discus
www.keystonediscus.com

[EthanCote.com]

Hi Brian,

I totally agree with you whole heartedly. I understand that the runt in my tank is a "normal" Discus rearing experience. I was just trying to illustrate the point that it appears environmental and behavioural seems to play a stronger factor in creating runts than genetic, since it appears everyone has runts in their tank.

Also your illustration of placing fishes that you don't quite like, also points to the fact that environmental and behaviour seems to have a stronger role in creating runts. Since if you didn't placed those fishes to take the abuse from other fishes, then perhaps you'll get runts out of your mix.

Have anyone here try taking runts out of the mix and place them in their own tanks and see how they grew???

Also if those of you that have runts, please list the conditions that created them so we can have a better understanding of how runts came about and perhaps prevent it from happening.


Cheers,

Chi.

[RAWesolowski]

My experience has been that environment and nutrition affect the ultimate size of a discus with a lower probability of genetics. That is to say, if you:

1. Do not overcrowd a tank,

2. Provide a clean, comfortable environment,

3. Feed them regularly with balanced nutrition,

You maximize the abiltiy of a fish to grow to its full potential.

The above conditions should be provided during the primary growth period for the fish. Once a fish is beyond its adolescence, it has a marginal capability to grow. From my reading and experience, the key gowth period extends to about 6 months of age. Once the fish is beyond this age point its growth potential is limited.

Often, fish purchased from a lfs suffer from deficiencies in all of the above categories. The store is unable to provide the same level of care as a hobbyist. Additionally, breeders often sell their lless than desirable fish ("culls") to the lfs.

[fcdiscus]

I also think you have a greater risk in Runts with imported fish. Ever notice how much bigger ther imported fishes ' eyes are than a comparable home bred specimen. It must have something to do with the quarentine and importers lack of proper feeding, which in turn leads to a lesser growth rate during the most important period of growth. Frank

i have also heard that most runts that breed produce fry that grow up to be big and beautiful fish, thus suggesting that in at least some cases, it is entirely environmental. I'm sure genetics are involved in some, but not all.
Brad

[Willie]

I find that 5% - 10% of every spawn will be runts. After about three months of growth, the spawns usually segregate out to three size classes: males, females & runts.

On closer examination, many of the runts are actually malformed. Usually, you can see some abnormality with the eyes. I've also kept runts in a grow out tank. The vast majority of them stay as runts and eventually die. Very rarely, I've had a runt grow out and become a small, but otherwise normal, discus. I've never had one that amounted to anything resembling high quality fish. So the only answer is to cull ruthlessly.

Remember that in nature, 1 - 2 fish surviving each spawn would represent species replacement. I'm not particularly surprised that defective fish would be produced in a large spawn.

Willie

[brewmaster15]

Hi,
I posted this else where a few weeks ago, but...


I think they only way you can know for sure if a runt is runted from genetics or environment is to breed them.


.....BUT
...........its not their offspring that you need to look at necessarily. Offspring from a genetic runt could appear normal(phenotype) if the defect is recessive (genotype). The only way you will know with any degree of certainty is to also raise the fry from the runt and then cross the fry. This will impart 2 recessive genes for the trait, and it will show in the phenotype. Note even this method requires you breeding large numbers of the fry, because the offspring that inherit the trait maybe as little as 25%

If the offspring of that runt are largely runted than the trait is dominant or the normal looking mate was also carrying a recessive gene for that runting.

Because of these complicated scenarios(which are far more complex than science has even really understood), Its best that anyone commercially or seriously breeding and selling their fish, not breed runts-imo. The True results may not be evident for 2 generations !

But now the question is ...what is a runt?


hth,
al

ps...

You can also tell if the runting is genetic by breeding 2 runts from the same spawn.

[che]

guys have you heard of salmons in norhtern part os u.s. that some salmon fries when they hatch drive away the smaller one's to the sea but ironically those salmons that ventured out on the ocean got really big and those are the stuff that gets served on the table when they go back to river or which they were born even though the two salmons look differnt from their size and still they're same species and even on salamanders water temp. dictates the size of the hatchlings warm water means more small once and a couple of big once which will cannibalize the small when need so my point is maybe controlling once size is a form of adaptation. like water with lo O2 level means more runts cause lesser cells in the body means less O2 consumption and the same goes with food and other subs. like NO2,NO3, and stuff hope somebody would do research on this

[mench]

I have several runts that are over 1 yr old and haven't gotten above the 3" size.I keep all my "runts" in a tank by themselves and always hope they will grow,and I use them when I set up a new tank...much easier to lose a little guy than a tank of fry or a pair....

Mench

[tyrancooper]

Quick question:

Do runts exhibit the same general appearance and size of normal discus, with the exception of size?

I am curious because I have 1 runt out of four juvenile blue diamond discus in a planted 40 gal breeder community tank ( lightly populated with tetras, two small clown loaches and 1 SAE.) The runt is relatively timid, spends most of its time in a corner in the rear of the tank, alternates from regular "blue diamond" blue to darker blue (but never black) and rarely eats.

Note: I have never witnessed the other three picking on him/her. The other three interact with each other and eat readily, but hardly notice the presence of the runt.

Tyra

nice genetic lesson Al!
thanks, as always

[wo]

I have two runts BD. They were purchased by mail March 2002. When they arrived I knew they were runts.( they had very big eye and only 2-inch bodies) But now they turn out to be my prettiest BD (their color and the reflection of their tiny fine scales are better than the rest BD) but small in size. ( only 10cm from head to tail ) I guess they could never breed.