This is from the article.
- Lethargy. This one can also be seen in more extreme halfmoons, but is extra common with rosetails and feathertails. Their fins are so heavy the fish can’t swim for long periods of time and often spend most of their day sitting on plant leaves or on the bottom of the tank.
- Broken fin rays. Fin rays are the thin bones that hold the webbing of the fin together. Towards the end of the fin these rays spread out, which is called branching. Perfectly normal, except when the fish is bred so that the rays branch out much more than usual. The excessive branching causes a bigger tail, which in turn puts more weight on the rays. When the tail gets too heavy, the rays will not be able to hold the weight any more – they can break, causing the whole tail to collapse and damaging the fish. Once this happens, the beautiful rosetail/feathertail effect is usually gone; you’re left with a fish with collapsed fins that is often unable to swim properly.
- Tail biting. One thing leads to another; to decrease the weight of their fins and move more freely, a lot of rosetail and feathertail bettas start tail biting at some point in their lives. This habit, where the fish simply bites off parts of the caudal fin, increases the chance of fin rot. It’s very important to keep the aquarium very clean if you have a tail biting betta!
- Premature death. Most breeders agree that there is something wrong with the immune system in a lot of rosetail and feathertail bettas. They are weaker than regular bettas and often the smallest of the fry – because all the attention goes towards breeding the fish with the best finnage, other problems* are ignored. This can eventually lead to premature death, as the fish is more vulnerable to disease.
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Rosetail Bettas are genetically weak from massive inbreeding and they are more likely to have health issues because of this. There was a thread recently about livebearers and inbreeding and Bettas are in the same category. See link below.
http://www.fishforums.net/threads/myths-about-live-bearing-fish.448518/
re: the article. Lethargy. Yes the fish have long fins and it does make it more difficult for them to swim. However, they are not in a river or creek with fast flowing current and they are not fighting other males for territory so that is nothing to worry about. If the fish are lethargic it is more likely to be from poor water quality or bad diet.
As for the big tail causing the fish to sit on leaves or the bottom, that's rubbish. Poor water quality will do that and so will disease. The tail is not going to affect fish that much because it weighs next to nothing in water due to being buoyant in the water. This is the same reason whales grow so big in the oceans. The water supports the weight of the animal.
Again, broken fin rays caused by having long fins. The tail has no weight pushing down on it in the water so that is not true. The fin rays might break more readily but that would be from inbreeding and genetically weaker fin rays caused by the mutation that creates the split Y shaped (branching) fin rays.
Fish do not naturally bite their own tail. That would be illogical to damage your main body part for movement through the water. It would be like a person biting their legs, it doesn't make sense in a normal healthy animal. If the fish are biting their own tails then they either have a psychological issue or a genetic psychiatric disorder that is being passed on from parents to offspring. Most likely the latter and this would be caused by inbreeding.
Premature death is highly probable due to inbreeding but has nothing to do with having a big tail. If the fish naturally had a big tail it wouldn't cause them to die prematurely. If they die young it's because they are stuffed up from being so inbred.
