Iron is often lumped together in the category “trace elements”, which isn’t altogether inaccurate given its concentration, but there is one important difference between Iron any most of your other trace elements: Iron is not optional. Running out of Iron in your system will halt photosynthesis and starve out your Corals. In many reefs, Iron is never a limiting factor, or takes a long time to become one, so it is often not diagnosed as an Iron Deficiency, but the start to a Crash that triggered a reset.
We target a level of 50ppm for iron but don’t go crazy trying to achieve this. we simply establish a weekly dose for our reef, usually starting at 25ppm per week, and ICP after 2-3 months.
If we’re over saturated, we dial back, if on level we would continue at the current dose, and if under 50ppm, we would increase our dose. Our weekly dosing is actually over 50ppm to maintain this level currently.
One thing that will complicate your relationship with Iron, or can push you from maintaining Iron simply with water changes and experiencing success, to running out, and needing to dose is Macroalgaes. Many macroalgaes use alot of Iron and can tip the scales towards depletion. We use Caulerpa in all of our refugiums because it uses far less iron than Chaeto.
To Paint a picture, lets go over the quintessential Crash resulting from Iron deficiency, it usually starts with a big growth spurt, followed by all of your refugium algae dying off, but the average reefer doesn’t fret – your corals still look great! But now your system cannot photosynthesize due to lack of iron, AND your reef has lost a major source of Nutrient export. The death of all of your macro algae may even have released previously absorbed nutrients back into the water column during decomposition. You fear you’ve missed Alk and Calcium needs, but test and find they’re actually at or even above what they should be, what is going wrong? Over the course of a couple weeks, your reef goes from plump and beautiful to withered, your Ca and dKH won’t move, and your nutrients won’t stay under control no matter how much you clean. And all of these issues triggered by the absence of a microscopic 50ppm of Fe in your Water.
It’s easy to forget about, so consider this your reminder!
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