Hello, first message in these forums. I am planning a 55 gal high light CO2 injected, dosed aquarium and am confused on whether I should use active carbon or not. Plants are my biggest interest with fish almost an afterthought. Can we get a last word on the use of chemical filtration and plant growth please? Thank you so much.

Here is my straight and forward answer to the issue:

YES! You should use carbon for new set-ups in order to remove NH4 and color bodies (carbon loses its adsorption capacity after a couple days but it can be left in place as it soon becomes good biological filtration media).
Routinely CLEAN it like you'd do with other media. BTW rinsing bio media is always MOST important IMMEDIATELY after you've messed your tank!!!

YES! After medical treatment! Discard it soon after (couple hours).

NO! For long-term use as long as you routinely substitute part (or all) of it by fresh carbon.
Plant health will decline after introduction of fresh carbon typically during a time frame of 3 to 4 days reflecting its trace removing properties even if it is a small amount of fresh carbon relative to the water body and even with daily fertilization.
The burdon of proof? Well, many years of observation of plant health and using GAC.


Best regards,
Detlef

I use it once every 6months to get rid of any metals, and when setting up a new tank, apart from that, it takes out the nutrients plants use.

I recall from research at "the Krib" that iron lasts a very short time in an aquarium, before the plants take it up. As I recall, people were dosing iron, then measuring how much was in the water and getting near zero measurements. The "expert" opinion was that the plants didn't allow it to remain in the water more than minutes before it was consumed.

If that was correct, or at least if my memory is correct, that tells me that activated charcoal in a filter doesn't get much opportunity to remove chelated iron from the water before it is used up. The other chelated metals in trace mixes may linger longer, and be removed by the AC.

Is this correct?

yes, i have also heard this too, on another site.

As far as I can tell even without using carbon iron drops out of solution within 4 to 7 hrs after dosing due to plant uptake, oxidation or precipitation (Testkit Dupla-Fe).

Regards,
Detlef

Depending on the chelator, KH, it will drop out of solution, I really do not think there is a large amount of uptake due to plants. Roger Miller and I talked about both ends of this topic in depth years ago.

Regards,
Tom Barr

Back to the topic: Detlef said is best in post #2.

Regards,
Tom Barr

Wow, thanks everyone. Im really glad I found this forum when I did (just weeks before starting my first high tech planted tank). I asked this question in other forums and got no answer or very scarry ones (like "carbon don't kill plants"). Again, thanks and I think I have found a new home.

I posted a little while back about a sudden deficiency in my hygro with new growth having leaf tips and pieces missing, almost like it was being eaten (but it wasn't). Traces were pointed to as the possible issue. Anyway, since then I suddenly realized that the deficiency showed up within a day or two of my adding activated carbon to the filtration, which I don't usually use at all.