For future readers, we should be clear that Seachem instructs what to use to safely regenerate Purigen. If the specific directions are followed, there is no reason to fear. Seachem STATES: “Use regular 8.25% hypochlorite household bleach (non-scented, no dyes, do not use a splash-less bleach).” In a FAQ post by Seachem, they also warn: “Seachem® has tested and developed the Purigen® regeneration instructions to be safe and effective when they are followed exactly as published, with no alterations, additions, or subtractions.” Do not use anything but the recommended bleach (this means not using more or less hypochlorite) as the Prime dose is specifically designed to act upon an 8.25% hypochlorite level.
You shouldn’t even use “splashless” bleach when washing your whites, as it does NOT sanitize. Their bottle even says that it does not sanitize. you might even argue that “splashless bleach” should not be called “bleach” at all, but this would limit their sales.
Careless consumers complained about the clothes they were wearing getting bleach spots when bleach splashed on them while they poured it in their clothes washers. So, Clorox supplied the fantasy of providing bleach that wouldn’t splash. To accomplish this, they altered the viscosity by adding surfactant (which also cleans - not sanitizes) and reducing the sodium hypochlorite.
For fishless cycling, just use pure ammonium chloride (it’s cheap). At the high pH levels used for cycling, the ammonium becomes ammonia.