i believe superthrive (with its hormones and vitamins) is used by growers to get roots going (say, before a re-pot). dont go crazy with this stuff (especially with plants with spikes) because ive read that the flowers can turn out deformed.
just a a couple of drops/gal and let the plant soak for 1-2 hours in the solution.
i use it myself (because there was a half-used bottle around the house) but i dont know if it actually makes a difference or not (because ive never not used it before repotting).
as for the fish, i use that too as a foliar spray about twice a month (i also spray the medium a little). my boyfriend always complains about the smell because we dont have the deodorized stuff. i think my plants like it.
nothings dead yet, but who knows, that could change.
if i were only to buy one thing, it would probably be the superthrive, though im hard pressed to say why...