black tetra not eating

Question
I have two black tetra, male & female, almost 3 years old. Tank size is 5 gallon, freshwater. Both have stopped eating, the female is occasionally eating a couple flakes (20% of former appetite) The male has not eaten anything for 2 weeks, is thin, I don't know how he stays alive.  He appears to have an appetite, tries to eat, but keeps spitting out food. PH is good, temp is 80, tank is clean, no ammonia.  I've tried breaking flakes into smaller pieces, tried a new brand , tried granules, tried a gel vacation feeder, Are they just old and senile?  Sometimes the male acts senile-he acts hungry, shoots to the surface to feed , then seems to forget why he went up there...and as I said, if he does manage to get a piece, he immediately spits it out.  The female also spits out food, but is eating about 20% of previous intake.  There is no visible evidence of disease-no rot, ick, white spots, fungus, rust color, red streaks, etc...Any advice?

Answer
Hi Mertis,

Your problem seems quite strange. Have you noticed a change in the outlook (body) of the Tetras in any way? If this occurred suddenly, there might be something outside the tank that is stressing them. I'd recommend that you add a slime coat enhancer, such as Stress Coat, by Api, and perform 10% water changes daily. The water changes will prevent any diseases, etc.

You could be right about the age - your fish have a lifespan of 3-4 years on average. Perhaps they are reaching the end of their life.

Good Luck, and Happy Fishkeeping!