Betta Sickness?

Ticked off atm because I had a beautiful male betta that died last night and I've no idea why.

He seemed perfectly fine a day ago. He was being kept in a small 15 l tank by himself with some cherry shrimp. I recently bought a new filter for the tank but the tank is very mature and I've had that fighter in there for more than a year now. It has a big piece of bog wood and some moss in it on gravel substrate. Also there is a green leafed plant growing up the back wall of the tank. I put well established filter media from my bigger tank into the new filter before switching it on. There wasn't room to leave the old filter in the tank too.

He was really lethargic last night when I went to feed him and was either swimming or dropping down to the bottom and hiding under a bit of the bog wood. It was like he was slipping in and out of consciousness really because he would go really still and then if he felt my gf try to scoop him with the small net he'd swim like mad for a bit to avoid it.

Normally speaking he was a blue colour but he had bits of red in his fins. Last night when we scooped him into a bag (to quarantine and also to use the only medication I had which was contraspot) his whole body looked quite red and his gills looked a bit reddish and raw even too.

I'm going to go and test the water now and will post up the results. The cherry shrimp seem to be fine but then again they live in the bog wood mostly (and reproduce like crazy) so I gave up trying to keep track of how many there are. (I just take some out and sell them when it gets out of hand

In the meantime...any ideas what might have happened? Are there common diseases or parasites that kill Betta's very quickly?

water test results:

Nitrate 0
Ammonia 0
Nitrite 0
pH 8.2 (always been very high)

I also should have mentioned that I always dose the water with the contraspot when I get new fish, not that that is relevant here because the only other things that are/have been in the tank are the cherry shrimp and they are all homegrown.

Maybe a parasite?

Betta are quite short lived,so a bit over a year would be a good life,some last a lot longer.
They are very prone to obesity,which,like in humans,can cause liver,kidney,etc problems,also helping to shorten the lifespan.

gutted for you mate its always a shame if any fish are lost to the big bowl in the sky. dont know much about betta but you did everything right when you put in the new filter so like Acara said its probably just age

Thanks for the comments guys.

I was careful to only feed a small amount of food to the betta and I also made sure that at least one day a week not to feed him at all (advice from SpookyMuffin) but I guess there were cherry shrimp in the tank and they seem to reproduce like bunnies, so its possible he was finding some cherry coloured new borns to snack on...

What surprised me was how quick he went. Like one day he was grand the next seriously knackered. Would old age or obesity onset, happen that fast?

Is there *any* chance there is a parasite of some sort in the tank? Any way for me to know?

The cherry's all seem fine but I don't want to go and get a new Betta and then find he's befallen the same fate.

Although siamese fighters do prefer a more acidic pH, they are quite tolerant especially if the tank was mature.

The lifespan is not great....especially for males. You say you had him for a year, I guess you wouldn't know how old he was when he was bought.

There comes a stage in the life of short-lived fish when one day they look great, but a bit aged, the next day they are dead. We see this with the true annual killifish (Nothobranchus and some south american mud-divers). What is even more noticeable is that the fish produce some of their most brilliant colours just before and just after they die.
If you look at an older male betta and compare it to a young one, you will start to notice the '150 year old trout' looking effect.

Of course there could be a reason other than age.....but that would need a bit of info on behaviour just prior to death and any noticeable things.

ian

Betta splendens only generally live for around 18 months (some shorter, some longer).
It takes quite a while before they are what the trade would deem to be a sale-able size so by the time you see them in shops they can be a year old, so you are probably doing quite well to to get a year out of one.
The amount of time the have to spend in the fish farm is one of a few factors as to why they are still quite expensive for one of the most mass-bred tropical fish.
Sorry about your fish. death is the only part of life that is guaranteed!