Treated some overwatered, root mite and gnat infested houseplants
with the commonly recommended 1:4 ratio H2O2 : water mix after
first letting them dry out for a couple of days. Damn if it didn't
bring
them back from the dead. They've gone from scrawny to flourishing,
in less than 72 hours. I'm tempted to give them a light sip (tsp
H2O2
per cup of water) every time I water them from now on. How much
is too much?

FWIW, yes, I read the earlier posts about how peroxide is a waste of
money in the garden, kills beneficial fungii, nematodes, etc. And I
agree. This is for decidedly inorganic container plants, however.