This information may help you. I found this on this forum.
http://www.amazon.com/exec/obidos/ASIN/086622288X/judysopeningmenu/104-3622357-2695909

1. Plastic can offgas toxins so perhaps glass container up to two gallon rather then 1/2.
2. Water temperature too low.
3. You don't say, but needs plants, note natural habitat, slow moving, 'weedy' rice paddy, canals, so on....
so perhaps a little pile of rocks with pebbles and some small plants or floating plants, as they like to sit atop them, also they like to pick at plants for food, and algae...

WW, I posted this on another thead, copied it here. With additions/deletions:

Natural habitat: Murky waters of the ...
Malay Peninsula and rice paddies of Thailand.
Wild B. splendens is perfectly at home in the standing, slow-flowing water and shallow, stagnant rain pools of his natural habitat.

Very interesting site with different experiences/perspectives:

http://www.aquahobby.com/gallery/gbetta.html

Others mention them doing very well in the proper sized, planted community tank with proper tank mates... some note a decline in health in larger spaces, and a preference for smaller (not the little bowls most mention 2 gal size at least) Guess it depends on individual and tank set up...

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Another interesting link (note one says this another says that, lol)

http://www.aquarticles.com/articles/breeding/Kick_Betta-keeping.html

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I personally am appalled every time I go to my local NYC petland and see a dozen or so little little small bowls lined up each with a Betta in it. They are listless, and dull and probably in their instinctive fish world, deadened. I once convinced staff to add a plant snippet to each and until the took them out with the every other day cleaning (which is the result of such a small space and a shock to the fish) they came alive, which they were not when thus isolated in those small lifeless bowls. Just by adding a small plant snippet, it was amazing how alive they became...

Just because Betta's can breathe from the surface does not mean this fact should be taken advantage of, ie kept in an isolated plantless small bowl or some such thing. (They actually utilize their gills, and only breathe from the top when their is no oxygen in the water.) The water will get soiled rapidly and frequent water changes as opposed to proper filtration stresses any fish.

They like to hide within plants and are a joy to watch in a larger properly planted tank. AS noted in one of the posts below, my male betta loves to hang out near the top of the aquarium within the floating types of plants.... Best to you, Sherry

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From Exotic Aquarium Fishes, Dr. William T. Innes (I found these editions on an online search, he was the best)

1 - Bettas need acid waters, about 6.8 ph.
2 - They do best in a well planted tank with liberal light.
3 - Water should be clean, clear, but with pleanty of natural sediment. (reference the rice paddy, slow moving water natural environment above)
4. the bettas do best on live foods.... (or supplement dried with, daphnia, mosquito larva, worms chopped, bits of fish, crab shrimp (not cooked) so on...
5. Males kept seperately, females can be kept together..
6. A single male may be kept in a community aquarium and possibly a female also, if the tank is a large one with plants for refuge.
Or, in general the sexes should be kept seperate (unless you wish to breed them) I always kept a pair in a medium size tank with lots of plants and hiding places.

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From another site:
The Siamese fighting fish is one of the worls most intriguing aquatic pets, and also the most misunderstood. These little fishy's are extremely territorial (the males being more than the females). It is true that the males will fight if kept in the same tank, therefor it is only wise to keep them in there own quarters. Females on the other hand can be kept together, along as there is a large amount of vegetation and/or hiding places in case there are "bully's" present. The truth is, that within every community tank there are "bully's" and after a while a "pecking order": will be established.

A misconception is that male Siamese Fighters are happy living in small cups of water. The truth is, they can survive, but are not happy at all, in fact, for a happy vibrant male, it would be wise to give him a larger home, for example, a gallon jar, or a small tank for himself, with a little vegetation (java moss, duckweed and assorted plant cuttings that will eventually develop a root system) for him to hide in and perch on (they are much alike the butterfly's of aquaria). Males can be happily kept alone with other species in a community tank.

Females are quite comfortable living in a community tank with each other. A word of caution is that some powerful filters will provide too much current for these fish, stressing them and tearing their fins. Females are quite drab usually less deeper in complexion than their male counterparts, however they do make good pets with a personality of their own. It is possible to keep one male with several females, but be warned and take caution in the word "several"

Plakat Thais/ Betta Splendens/Siamese Fighting Fish love to be fed small live foods such as mosquito larvae, bloodworms, whiteworms, and wingless fruit worms, however they can also take pellets and flake. The key to a succesful diet is a varying diet that is full of nutrients.

Siamese Fighting Fish are not fussy when it comes to water quality. In nature they are found in small rice paddy's that are exremely muddy. However it is advisable to provide them with clean, dechlorinated, aged water. If you are going to take water quality a step further, Reverse Osmosis water is near perfect and black water extract will provide close to natural South East Asian Water.

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Betta's need warmth!!!

Unless you live in the tropics or in the warmer parts of Asia such as Thailand and Singapore you need to keep your bettas in a heated tank. If the water is not warm enough the fish are susceptible to Ich and other diseases. You will not see alot of movement in them and they will be plain unhappy.

Bettas are carnivorous and love to be fed. A healthy betta will eat, an unhealthy betta wont eat.!! They love live foods like Blackworms, mozzy wrigglers and brine shrimp. The next best thing is frozen food which are easily available at pet shops or you can freeze your live foods yourself. Most bettas will accept dried food also. Its best to give them a mixture and not just one type. If they seem to be constipated or their swim bladder is playing up - as in they are floating up the top on their sides or sinking to the bottom. peel a thawed pea and chop it up. They love them and it should fix the problem.

They like their water clean!!!

To avoid diseases and unhappy Bettas ensure your water is clean and healthy. Depending on the size of the tank you have them in.

If you have them in a larger tank such as a 2 foot tank and it has a filter going you can probably get away with a 25 to 50% clean once a week.

(again, when I raise fish with outside filtration, and healthy growing plants, cleaning is less often needed - so judge by the situation/environment.)

The simple answer is Bettas get sick if their water is filthy.. they are swimming around in their own muck.

Plants make them happy

Bettas dont eat plants but they like to hide in them or lie around near the surface on them. Plants given that their healthy improve the water quality by soaking up the Co2 in the tank. If their unhealthy and rotting away they become part of the problem.

Gravel is not needed in a betta tank. Its good to anchor the plants, its pleasing to the eye but unless in a big tank with other community fish its a hassle to clean the bottom. (again I disagree here, if plants are well established and growing, the root system keeps the soil healthy and also bacteria that grow there and just as with ground soil, soil organisms keep things healthy) Its a lot easier in smaller tanks to syphon up the muck on the bottom to stop it rotting into the water to not have gravel. Its also easier to see when a betta does a poo and if theyve eaten all their food. Hence noting if the fish is healthy.

Male bettas are solitary from their own breed, by this I mean dont be putting a male betta with another male betta as they will fight to the death. Only put him with a female betta if your intending on breeding them and take her out once the deed is done. One male betta may be placed in a tank with other community fish, as long as they are peaceful fish Mr Betta will do fine. Female bettas can be placed together fine, my experience is more than 2 is harmonious. If only 2 are in the tank they will spar to get the top ranking. In a community tank with other fish they do fine.

Alot of fish shops will tell you that Bettas dont need a lot of water so they can live in a cup or something small. Bettas can survive in this environment, it doesnt mean they are happy. As long as the water is kept at the right temperatures and kept clean they can survive. Bettas like all fish like to have room to swing a cat in so to speak. My adult males are all kept in 3 litres of water and if i had more tanks and more space they would get more. My juveniles are kept in coke bottles be it 2 litres or 1.25. As they are smaller they can handle this and its temporary until they are sold. Im sure they are all thinking .."When's it my turn?"
Also, there is a plant site whereby wood with plants anchored to the wood ( or stones in some instances) would be a nice addition to a container with a Betta... link below...

http://www.tropica.com/default.asp

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They loved the warm water! The temperature can be up to 90 degrees Fahrenheit. None of them sink to the bottom. They swim around and They eat good. They did not get sick. I find that Bettas get sick if they suddenly get chilled. I tell people to keep their Bettas in the warmest and quietest place in their home. I have been doing this for many years. If someone else in the store has to put the Bettas in cups or moves the Bettas to a bright and noisy location in the store, the fish die.

My betta had similar shredded fins and it was because his fins got "sucked" into our power filter. I, following a friend's recommedation, put a cut piece of panty hose over the filter and it hasn't happened since.
Hope this helps!

Ship:
You don't say if there are other fish in with him. If there are, they are most likely the cause. I've never had one of my own rip his fins but other "nippers" have done a number on some of them.

Do you have a power filter? Could he be getting stuck?

I agree daylilyluver,
If thee are other fish in the tank, one or more fish are pulling the Betta's fins.
Theresa

you didn't mention what size tank you have, or what kind of decorations you have, is it possible he's catching his fins on sharp edges in the bowl/tank? i would remove any questionable decorations and use some stress coat, and see if that helps.

also you may check for external parasites, if you notice your fish swimming erratically or trying to scratch his body and fins against objects in the tank it may be parasites. i got that helpful information (about the parasites) from www.bettatalk.com

He is in a 2.5 gal tank with no others except a snail. I try to keep live plants in the tank,a s well as a permantent plastic one so that he always has a place to hide. I tried adding a background so that he would have more privacy, but it increases the reflection in the tank and he spends all day flaring. I think he has gotten used to it now. I alsp have real shells from the Gulf of Mexico in the tank, and a power filter that I believe he is not getting stuck in. I don't think he could fit underneath it. He seems to be very happy, except that his tail just will not stay in a good condition.

Are you sure you don't have finrot??

Tails will regrow in time after finrot, but you have to treat the problem first.

My suggestion is to remove your real shells...they may be affecting the pH of the water and stressing your fish.

Since your tank is relatively small the water parameters are more likely to be easily influenced by even small changes from things like shell, plastic, temperature...possibly even fumes in your home.

Poor water conditions or constantly fluctuating conditions can contribute to problems like what you describe.

This sounds like Ick to me. Any white spots (like the size of sugar granules) on him?

Ick is pretty easy and cheap to treat. 2 bucks at a pet store and it can be cured in a couple days.

You have to be very careful what goes in the tank. My betta caught ick from a STERILIZED (said it on the package) silk plant.

There are three (four?) reasons why bettas chew on their fins. Don't worry, this is a very common occurrence, and Melafix will heal up his fins in no time (unless he's like my fish, who hates Melafix and will chew even more whenever Melafix is in the tank).

First, your betta may be bored and understimulated. Have him flare at a mirror or move your fish a more trafficked area of the house to stimulate him.

Second, your fish may be overstimulated and is effectly chewing his nails in sheer anxiety and nervousness. Move him to a quieter location, and don't startle him by turning lights on and off suddenly.

Third, he may require a differently-sized tank. Usually people can solve the problem by doing one of the two things listed above, but it's also possible that he's not happy where he is. My fish never chewed on himself while living in a temporary 1/2 gallon, but when he moved to the 2.5 he'd chew constantly. In fact, he just did it today. Speaking of, your water may be dirty, and he may be chewing it as a result. I know that if I see my fish's tail in ribbons, that means I have to change the water. (he's picky and sensitive, which means I do a 50% water change every 3 days. The things I do for my fish!)

He may just be a chronic tail-biter. If it comes down to that, Melafix and salt are your two best friends.

If you have a female betta, she may eat his fins at night. My princess peach ate two males before i realized it was her. She is big and tough and eats males fins for a late night