2 weeks is not good. Since the fish isn't eating I would try epsom salts for 2 days max. (Epsom salts is my prefered method to peas since most times when fish are sick they don't eat, try both peas and epsom if fish is eating) Read the attached article from fish doc. Worse case it's an infection. I am not lecturing you but for benefit of others, tropical fish stand a better chance in a properly heated, "cycling" aquarium of 5 gallons or better. Without proper water temp. they are more suseptible to disease and parasites.

Any signs of ich or gill infections? Have you changed his water? Try some live brine shrimp sometimes it triggers their hunting instincts. I wonder if it could be old age?

Angalee, I agree with woesime on larger heated filtered tanks for bettas which need a steay 80 degrees or so. (mine are in 2.5 gallon, small filter, heated, and java moss and anubias plants - doing fine, in larger they don't do as well, although I have seem them in much larger tanks. My females do well in larger community so I think the longer taled males can run into trouble. My one guy now well in the smaller ran all over the 20 large so fast his tail got whipsawed and then fin rot, so depends. Always exceptions, but they need the same care as any other tropical fish, with regard to heat, filtration and as little stress as possible, and in smaller bowls with more frequent water changes et al, that is stressful.)

That said you've had your guy for one and 1/2 years so he was in good hands. So I am leaning towards older age as a possibility, if you've ruled out fin rot, so on. Most (not all) are about one year old when purchased (I just found out that petco's are pretty young and look it, ie not discards from breeders as older ones are). So, in this day and age, 2 1/2 years is considered old. (genetic in breeding weakness so on have shortened their lifespans).

But to rule out things: Did anything different happen two weeks ago? From the usually routine. Again, unless something drastic, the fact that you have had him for a longer time with no problems causes me to think it is old age.

I'd say keep him comfortable, as at this stage without any discernable illness (ie fluffy white stuff, fin rot so on) most likely he is tired and at end of life. Forget feeding (but try to offer if you feel like it), but use turkey baster to clean up fast if he refuses. Stress free, lower lights, just make him comfortable. Like all creatures the body starts to break down and food is not needed. It may sound silly but when mine are dying I just stick around a bit and thank them for the joy (or grief! lol) they gave me. He is your pal I know. Best Sherry

hi,
I am planning on purchasing a 20gal. tank and I was wondering if I could put a rainbow shark in it. if so what fish and plants would best suit the shark?