I put up a really large garden for the summer and I can go through anywhere from 40 to 60 gallons of water daily from the fish room from mid-May right through October. While all the claims are 100% correct in the case of the vast majority of houseplants, it isn't doesn't necessarily preclude fertilizing garden plants. It certainly doesn't hurt (my string bean crop will attest to it!), but it's rather difficult to measure as opposed to an organic fertilizer with a recommended per sq. ft application rate.
"Why can't my wife see all of this stuff as an investment?"