"Dave M. Picklyk" empowered us with this mighty blow
against the Patriarchy:

I got an iron test kit today and found out that I do not have any
amounts of traceable iron in my 48 gal. planted tank. I've added some
liquid fertilizer that is iron-enriched. I've tested the water again
in a hour and there is about .35 to .4 mg/L now...which I've heard was
good.

Is liquid fertilizer a good way to supplement iron to a system? How
long will it be till I usually have to add more in? (Or I can continue
testing every 3-4 days for chelated iron levels)

You might find this helpful:

http://www.csd.net/~cgadd/aqua/art_p...izer_intro.htm

(along with the other articles at Chuck's website!)

I add Tropica Master Grow and am happy with the results.