Iron is not a nutrient that's needed in high amounts for a tank. There's no real reason to dose more than the bottle says because it only takes soo little to keep the plants happy.
Yeah, but the bottle doesn't really say. It reads:
Use 1 capful (5 mL) for each 200 L (50 gallons*) or as required to maintain about 0.10 mg/L iron.
Notice even if you think the does is specified there's no time frame mentioned - daily, weekly, etc.
There is another PDF I found from them, here:
http://www.seachem.com/support/PlantDoseChart.pdf
that says to dose 6 times a week, but there's no indication of whether this is for high tech, low tech, EI, etc.
That's why I tried to test, as the only real guidance that was clear is "maintain 0.10 mg/L". Which with any dose similar to this you just can't do.
Here's another quote from Seachem just to muddy the water further:
Though iron is technically a micro-element, plants take it in very readily. In fact, you can dose Flourish Iron and then test your water for iron shortly thereafter and find that not much remains in the water, as your plants will utilize so quickly. This also has a lot to do with the fact that it is in the oxidation state that plant cells prefer(ferrous) and is complexed with a gluconate that can be utilized for growth.
So I just decided a cap full a day is the right amount.
