Sounds better than my thumb rule. 10,000 uF, even if it is more than one capacitor.That's sort of true but mostly for low voltage power supplies where a less than half a volt ripple at 120 Hz accounts for more than 5 - 10% of the working voltage.
At 160 volts that same .5 volt ripple would be tiny and the 100,000 uF 200 volt capacitor bank to make it so a rather spendy unit to build thus going by percentage of ripple to system nominal working voltage allows for a much lower capacitance to be used.
By my estimates a 10,000 uF bank would be more than sufficient for an unregulated 100 amp capable electrolysis system like the OP wants to build.
40,000 to 60,000 has also been suggested, so there is his range; 10,000 to 60,000, whatever he can find.