"If you carry developer over into the fix you can get staining,
especially as silver accumulates in .... the fix. An acid stop
bath puts a stop to that, so to speak.
With an alkaline fixer it is necessary for a really good rinse
between the developer and the fix."
As Lloyd has pointed out a short acid stop bath is no more
effective at washing out the developer than an equally short
water rinse. The reason for an acid stop is the acid fix. Save
for some very rare exceptions an acid stop and acid fixers
were/ are a necessary marriage. STOPPING I believe is,
for any practical purpose, equally quick acid or water.
"Another fix is to use the fixer one-shot."
My solution; following a very dilute developer a very
dilute one-shot fix. Drop Stop, Develop - Fix. Dan