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 Facts and experiments about runts  

                                                                                     author: Faith
                                                                                                                  date: 08/12/02


All bettas are not created equal

 One thing that has always puzzled me when raising a spawn of bettas has been the severe discrepancy in growth between siblings. At first, it seems all little fry are born equal. All usually hatch at about a few hours interval, all seem to become free swimming on the same day. All start stuffing their little faces with baby brine shrimp and other yumminus live foods in unison…Yes, it seems mother nature equally gives a chance to each and everyone of them to thrive and live, spreading its blessings equally across the board.

 Or is it? And if so, then why do some bettas grow and blossom so much faster than their siblings, while others, the RUNTS, seem to be literally left behind? The older the fry get and the bigger the discrepancy between the sizes. Then comes the crucial week, you know, that week when all of the sudden, betta fry turn into bettas. It’s like they suddenly EXPLODE, metamorphosing before your very (amazed) eyes. And that’s when it starts to become painfully obvious: Some bettas switch to 4th and 5th gear, while a few others seem to be left on the road side. Pass a few more weeks and there you have it: on one hand the beautiful, blossoming, proud, flaring, round bellied lucky ones, and on the other the tiny, skinny, timid, ugly ducklings also known as ‘RUNTS’.  These less fortunate spend their time hiding in the corners, bullied around by their larger siblings, and barely able to get any food at feeding time. As time goes by, their health seems to deteriorate and they start dropping dead one after the other, until none are left. Worst yet, if they do not die of their own, they end up on the menu of one of their brothers or sisters. I will never forget the sight of a betta swimming around with a tail sticking out of its mouth. Yop, it had gobbled up one of his little brothers (or was it a sister?) L((((((((. Since that incident (it was my third spawn, I remember), I have learned what to do to prevent this from ever happening again. One of course might argue that it is nature’s way to insure the vigor of a line, and that “survival of the fittest”, in the end, works for everyone’s best interest. The best bettas live and then in turn procreate, while the ‘not so good’ ones are wiped out.  

Often times, if nature does not do the job fast enough, the breeder is happy to step in. I heard of this one breeder who fishes out unwanted bettas and tosses them on his lawn. “Lawn fertilizer” he explained to one of my friend. I was quite disturbed by this and have to say bluntly that I cannot respect any human being who does not show compassion. Many people are eager to ‘get rid’ of their runts (either by giving them away or by plain killing them  L(((  ) and by so doing may very well be shooting themselves in the foot (see below).  

So let me step in and put in my two cents worth and tell you my theory about runts, why they come to be, why they can be useful, and why they should be treated with respect.  

My observation on the matter has been the following: There are basically two types of runts. The slow growing/blooming runts and the genetically defective runts.



The slow growing/blooming ‘runts’  

When breeding canaries in the eighties, I quickly learned that out of four eggs, laid at one day’s interval, one egg would be last to hatch (well, duh!). Usually the first two would hatch the same morning, while the third might hatch later that day. Then the next day I would end up with an extra chick, the last of the batch, the one that came from the egg which was laid last, the “unlucky” one. That fourth chick would rarely make it. Was it because the 4th egg systematically housed a genetically defective chick? Think about it for a moment: What are the probabilities of this being an accurate statement? No, indeed the chicks were genetically sound and should the other three eggs have not hatched first, that fourth chick would have had a long and prosperous life. Instead it would often not last more than a few days. Why? Well, because the female would feed the chicks according to which little beak was highest and most open. The first chicks hatched being a bit larger, (because they were a day older) would be competing for food more aggressively and get fed more often than their smaller, weaker siblings. The smaller chick should get more food to catch up, but instead gets less and consequently grows even slower and becomes weaker and weaker, to the point where it no longer has the strength to stretch its little neck up at feeding time. Furthermore, the small size of the nest would cause overcrowding and soon the runt of the batch would be trampled and end up smashed under the weight of its three other siblings. And invariably, I would then find it dead. L

 Well, bettas lay a lot more than just 4 eggs, and a 10 gal tank filled halfway offers a lot more room than a tiny bird nest, still the same phenomenon is observed. Some fry grow a tad bit faster than others, and in so doing soon take over the tank. Since bettas usually take up to 4 hours to spawn, and since eggs are laid by batches, it is very probable that the eggs that were laid in the early batches do hatch a few hours before the eggs laid towards the end of the spawning ritual. It is also very probable that this few hours difference at the starting point may in the end make the whole difference in the world. Bettas that have hatched first will eat first and as they grow SO fast, that extra few hours head start will give them a slight size advantage. As hundreds of hungry little mouths compete daily for food, a size advantage must be a decisive factor in who survives in the end, and who doesn’t. As days go by the discrepancy in size and ability to get more food becomes increasingly noticeable and overwhelming. The larger the spawn, the tougher the competition and the more runts you will get.

 Another factor that come to play is the fact that some bettas will simply grow faster, period. Perhaps they produce more growth hormones, while other produce less. I am sure that if you take two fry that hatched simultaneously, you’ll find that one will grow faster than the other. Just as you have the slow growing runts, you also have the abnormally fast growers. You know, the bettas that stand out like a sore thumb, the ones you have to pull out and jar weeks before anyone else because they are so overwhelmingly bigger and blooming faster than anyone else in the tank. Surely they did not hatch weeks before the rest, so that is where the growth hormones theory kicks in. I had one of these in my very first spawn, and called him “BIG DADDY”. Big Daddy was about three times larger than all its other siblings, and I am sure, ate quite a few of them on the way to its Guiness Book of records size! LOL.

 Another experience that in my humble opinion confirms this theory, is a spawn I once had where only TWO bettas survived. Most breeders might have simply tossed the spawn but I couldn’t bring myself to. So I raised the two fry LOL. Needless to day these two shared a 5 gal tank and had plenty of space and more food than they knew what to do with. So I assume the competing factor did not come to play much at all. Still, one fry soon became overwhelmingly larger than the other, almost three times bigger, and soon started to systematically chase around and beat up its smaller sibling. So much so, that I had to separate them. Both grew to become beautiful opaque males and although one blossomed much faster, the other eventually caught up over the months and in the end turned out to be even more beautiful than its brother.  

And that’s another thing with slow growing runts: If given the chance and the extra time, they too will blossom into equally beautiful bettas. Furthermore it has been my observation, as well as the observation of many seasoned breeders out there, that sometimes, many times, the slow bloomers turn out to be the best of the batch, color or finnage wise. Discarding them results in losing possibly what would turn out to be the best of the spawn (although not the fastest blooming ones).


The  defective ‘runts’  

In the case of defective bettas, things are quite different. Hatching time plays no part and growth hormones are a secondary factor. What happens here is the fry has some genetic defect that impairs its ability to swim, eat, or be competitive enough to grow normally. Such defects may be: A crooked spine preventing it from swimming properly, a short body or other malformation of the body, malformation of internal organs. The later you cannot see, but these fry affected will not eat and end up starving to death. These will usually be wiped out over the weeks, and you may find them dead at the bottom of the tank, one after the other, until none are left.  

Sometimes a fry may not be genetically defective per say but simply not healthy. Perhaps it has a weak immune system and tends to become infected with any bacteria resident in the tank, while the other fry seem unaffected. Such fry will not last long.


Learning to differentiate between normal runts and ‘defective’ runts  

As a breeder becomes experienced, he or she will develop the “eye”. That precious, experienced eye will be able to tell healthy runts apart from defective ones. You will learn to scrutinize a smaller betta and detect early signs of spinal defects, body malformations, gill problems, diseases, etc… It is vital to keep a close eye on your spawns. A good breeder will quickly come to the rescue of fine bettas that are at a disadvantage in a spawning tank. He or she will even out the odds and take appropriate steps to insure everyone in the end has a chance to show their full potential. (see below). He or she will know to not breed the defective bettas and will know to nurture the ones that have potential. This of course, can only be achieved with the years. If you know an experienced breeder, you may ask them to help you and give you pointers by inviting them over to your fishroom and have them do this selective process for you and explain to you how and why they evaluated the fry the way they did. (Throwing in a nice dinner may be an appropriate gesture on your part). Joining a betta club or IBC local chapter may also be of great help.


Experiments with  normal runts and ‘defective’ runts  

I experimented with jarring runts to give them a chance to grow and make it. Invariably I have found that the healthy runts would promptly blossom and catch up with the rest of the spawn still in the tank. On the other hand, the defective runts still would not eat and eventually end up dead in their jars.


How to rescue your  normal runts

 Here are a few tips to help even out the odds in your spawning/grow out tanks:  

bullet Provide plenty of hiding places: These include lots of plastic or real plants where the fry can find refuge.
bullet Provide plenty of growing space: the less fry in a tank the more even the odds will be. If your spawns are large, divide the fry and place them in two or three tanks. The more crowded the fry the more the runts and the less their chances of surviving.
bullet Distribute food evenly: when feeding the fry spread the food evenly in the tank. Make sure to drop microworms in the four corners of the tank and in places where you know some of the smaller fry hide (plants, heaters, etc…). This does not imply you should overfeed and let food rot in the tank.
bullet Give plenty of food: make sure everyone can get some and that some is left over for later. This does not imply you should overfeed and let food rot in the tank.
bullet Separate runts: as fry grow, it will become necessary to segregate runts. The best way is to use a fry separator, or whatever stores call these now a day. I call it a fry coral J. It is a square plastic structure with a fine fabric mesh covering all it’s side, expect of course the top. It hangs inside the tank, and the water can flow through it but the fry (even the smallest ones) cannot escape. Small fry can’t get out and big fry can’t get in. Food can be dropped inside, but in the case of microworms, I recommend placing a computer transparency sheet on the botton of your coral, cut to fit. It will prevent the worms from falling through the mesh bottom.
bullet Jar runts: have a few extra jars handy to jar runts that are bigger. In a jar a runt will be safe and have no competition when it comes to food. It will promptly grow and catch up.
bullet Be patient: some runts may take time but they may turn out to be your best bettas. So patience can be rewarding!


What to expect from your normal runts

 Runts may save the day. A runt may blossom to be the only black/white BF of the spawn, or the only halfmoon male. Runts blossom slower so they are hard to sex and oftentimes the late blooming males are thought to be females. I received two such females which turned out in the course of the next 5 months to be two of the most beautiful males I own! One small DT blue female turned into a gorgeous HUGE DT steel/white BF with a perfect pattern and beautiful finnage. The other, a smaller DT marbled female, turned out to be a rare red/white/black marbled male of breathtaking beauty. Had these runts been turned into lawn fertilizer, we would have missed out on two top fish. And yes, mind me, it did take them a while to get there, but they did get there, on their own time. Sometimes runts do not turn out to be ‘special’ and may even look unappealing, still they can make wonderful pets and all should be provided good loving homes.  


Well, now you know almost as much as I do and I hope this E-Magazine article will help you exercise better judgment when it comes to each of your runts.  

Because you never know: the ugly duckling might very well turn out to be your only swan...

A footnote from Faith:

I wrote this article while recovering from my surgery last July. As you can see I had a lot of time on my hand LOL !