Is my 20-year-old sourdough depressed?

When a starter is out of whack - such as this - all you can add is flour - and a good amount of finger crossng. This happens over time - eventually it'll get out of sorts and get to acidic. I've said before - and it bears repeating - little starter - lots of food - time. If it doesn't fix itself - start again. Enjoy!

Water could be involved as you speculated. Get a bottle of drinking water and try that.  I remember on another thread that someone posted that some bottled waters aren't good for sourdough and some are. If that's actually correct you may have to try several varieties.

Of course that may not be the problem.  Starters can get sick; maybe some other organism got to growing and out-competing the yeast.  That would be most likely if your starter didn't get very acidic any more.

Basically just try to nurse it back to health, which could take several weeks.  If you feed it and there isn't much activity, then discard some and feed it again, you could be diluting the yeast and bacterial concentrations, which is the opposite of what you want.  You want a good growth of lactic acid bacteria to drive down the acidity and prevent other organisms from flourishing.  And, of course, you also want to encourage the yeast to grow. So don't feed it again for several days after a feed unless the starter shows strong signs of activity and growth. Stirring the starter once or twice a day is generally helpful.

If this all works after another week or two, it might have been equivalent to creating a new starter.  It's hard to tell at home whether the old starter revived or a new one got going.  And who cares, really, as long as a working starter is the end result.

TomP

Some Sparkling Perrier or San Pellegrino water. If water is the issue your starter will love this special treat. 

Here in the U.S., municipal water districts may add chlorine and/or chloramines to water supplies without advance notice, whether the primary source is well or surface. This can happen when harmful bacteria contaminate the system or just a branch of the system. Like oh say when torrential rains and flooding cause waste water to overflow, maybe during a hurricane? 

These chlorine compounds could weaken or "sicken" a sourdough starter or even kill it in a worst case scenario.

Just a pint of bottled water will make a lot of bread and should eliminate one variable in your starter mystery.

Best wishes. Dave

ha! I wish drugs would help!

here's my starter depression story. It's 100% rye and only 3 years old but we have gone through some wars together.

It took a long time to get it started and I nearly threw it out several times, but finally it worked. I also dropped the glass jar it was in & rather than risk glass chips in my bread, reconstituted it from a spare that had languished in my fridge untouched for more than four months.

Its first bout of depression came because I was underfeeding it. Solution: I bought a scale.

The second bout was from some flour that was somehow degraded. It was a national brand of organic rye and well within its use-by date, but it stunted my starter & all my breads. Solution: I threw the flour out and switched to an organic brand that was fresher because it was grown within my state.

The third bout took a longer time to figure out -- and you might say the starter & I are are still in therapy to this day. It wasn't that the flour ceased to be active. The problem was that it was too active and that my timings for levains -- which had previosly been tolerant of scheduling glitches -- suddenly had to be incredibly precise. Otherwise, my breads would spread uncontrollably in the oven. I tried bottled water -- but it did nothing. I tried a bunch of 1:10:10 feeds, which helped regulate things a little. Finally, I queried the miller because I had a sense the last few bags of rye flour had been finer that I was used to. And, they confirmed that, though they hadn't intended this, it was possible they were producing a finer flour because they had recently added a new millstone.

My current theory is that the finer flour ferments quicker -- and that the starter and any levains I make with it rapidly get so acidic that they tend to inhibit yeast growth and break down gluten. 

We -- the starter & me -- are still working this out.

Rob