Activated carbon stripping trace elements

Makara23 · Jan 30, 2023

My macro algae grows very fast and it's quite obvious after it consumes all of the trace elements it needs to grow. This is when it starts to deteriorate. When I dose small amounts of ChaetoGro, it perks up the next day.

I want to start using activated carbon to remove odor and possibly toxins from corals. But will carbon media also soak up the trace elements from ChaetoGro? Will it also remove organics that the filter feeding hitchhiker and corals eat?

Chemical composition of ChaetoGro:

potassium (1.3%)
boron (0.009%)
carbon (0.005%)
calcium (0.14%)
chlorine (0.39%)
iron (0.32%)
magnesium (0.4%)
manganese (0.0475%)
molybdenum (0.004%)
cobalt (0.0004%)
nickel (??)
sulfur (0.16%)
zinc (0.002%)

vlangel · Jan 30, 2023

Makara23 said:
My macro algae grows very fast and it's quite obvious after it consumes all of the trace elements it needs to grow. This is when it starts to deteriorate. When I dose small amounts of ChaetoGro, it perks up the next day.

I want to start using activated carbon to remove odor and possibly toxins from corals. But will carbon media also soak up the trace elements from ChaetoGro? Will it also remove organics that the filter feeding hitchhiker and corals eat?

Chemical composition of ChaetoGro:

potassium (1.3%)

boron (0.009%)

carbon (0.005%)

calcium (0.14%)

chlorine (0.39%)

iron (0.32%)

magnesium (0.4%)

manganese (0.0475%)

molybdenum (0.004%)

cobalt (0.0004%)

nickel (??)

sulfur (0.16%)

zinc (0.002%)

I am not strong in the chemistry aspect of aquaria, but I keep a lot of macroalgae in my display for both the ornamental appearance as well as the nutrient uptake. I also use about 3-4 Tbsp of carbon that I change out weekly along with filter floss. I dose Coral vite weekly to replenish trace elements and occasionally iron, and Flourish. I have not noticed that the macroalgae are impacted by the use of carbon.

Randy Holmes-Farley · Jan 30, 2023

Many trace elements bind organics and those organics will be impacted by a variety of Reefing practices such as GAC and skimming, but I do not think it’s a reason to avoid GAC, and the info brought to bear on this question from freshwater and wastewater tests of GAC are likely misleading for seawater where there is far more competition from binding sites on gac from all of the other ions. .

taricha · Jan 30, 2023

I think of it this way. If I look at what collects in my skimmer cup and ask what elements are in it?, I would conclude that many "good things" got skimmed out.
However, I'm going to run the skimmer anyway. Because there's much more undesirable stuff that I'd rather got removed. And I can accept or correct the lower levels of "good things" as a result of skimming.

I feel the same about GAC.