# Filter carbon and fertilizers



## hoppycalif (Apr 7, 2005)

I keep reading that activated carbon will deplete the fertilizers we use. I doubt that being true, but it would be very easy to test. Just get a small tank of water, put a HOB filter on it, with activated carbon in it. Add some KNO3 and measure the NO3 with a test kit. Run the filter for a few hours and retest for NO3. Then repeat with KH2PO4, testing for PO4. It would be much harder to test the effect on the chelated micronutrients, but an iron test might work.

Has anyone done this? It would be a week of fun at the most.


----------



## JamesC (Jul 26, 2005)

I doubt it is true either with regard to nitrates and phosphates. If it were true there wouldn't be such a big market in nitrate and phosphate removers if activated carbon could do the job. But with the traces I would guess that there is a possibility of their removal, but it is only a guess.

James


----------



## JamesC (Jul 26, 2005)

Came across this Activated Carbon removal table which may be of interest.

*High To Very Good *

Arsenic, bleach, chloramine, chlorine, chromium, colors, dyes, gold, insecticide, odors, monochloramine, tin

*Good To Moderate*

Acetic acid, cobalt, detergent, hydrogen sulfide, mercury, ozone, potassium, silver, soap, solvents, vinegar

*Fair*

Copper, iron (not chelated), lead nickel, titanium, vanadium

*Low To None*

Alkalinity, ammonia, barium, carbon dioxide, hardness, copper, manganese, nitrates, selenium, molybdenum, zinc.


----------



## davemonkey (Mar 29, 2008)

That seems to suggest that one migh thave to worry about Potassium defficiency with fresh activated carbon, but not much else.


----------



## hoppycalif (Apr 7, 2005)

When activated carbon removes potassium, for example, I assume it is removing the K+ ions, by attaching them to the carbon. If so, what happens to the NO3- ions from KNO3? Do they gain a H+ ion, leaving the water with a lower pH? Or does the H+ ion come from the water, leaving an OH- ion to attach to the K+, which is what is held by the carbon?

Look at this as a chemistry lesson for the slow learners!


----------



## jazzlvr123 (Apr 29, 2007)

seems like a novel idea. you should create a control ant test this theory out if you have the time hoppy this would be a very interesting study also a great topic to review at the next SAPS meeting 

sorry i couldn't fly out for last nights meeting haha  how did it go?


----------



## hoppycalif (Apr 7, 2005)

jazzlvr123 said:


> seems like a novel idea. you should create a control ant test this theory out if you have the time hoppy this would be a very interesting study also a great topic to review at the next SAPS meeting
> 
> sorry i couldn't fly out for last nights meeting haha  how did it go?


We had two of us, then two more joined us out on the sidewalk as we were leaving. Not one of our outstanding meetings.

I don't have the test kits to do this test or I would be doing it. I suppose I could buy them, but I would want the good ones and they cost quite a bit, as I recall.


----------



## Edward (May 25, 2004)

Carbon removes organics, not elements like metals and salts etc unless they are bond to organic molecule. So, odors, colors, tannins, chlorine, gasoline and some aquarium trace elements are effected. Basically, not very useful in an aquarium.


----------



## Left C (Jun 14, 2005)

Is phosphate included in the detergents listing? It's not listed anywhere else.

Good To Moderate

Acetic acid, cobalt, detergent, hydrogen sulfide, mercury, ozone, potassium, silver, soap, solvents, vinegar


----------



## bigstick120 (Mar 8, 2005)

It was my understanding that carbon was bad because it removed trace elements. Not KNO3 and other macros


----------



## hoppycalif (Apr 7, 2005)

The metals that are trace elements are usually all chelated, so they are organics. I still wonder if they are actually removed, or if this is just a theoretical possibility.

Another thing, iron, for example, is quickly taken up by the plants when chelated. People who test for iron rarely see any unless they test immediately after dosing. So, that tells me that iron, at least, does not stick around in the water long enough for the filter carbon to ever remove it.


----------



## V.PooH (Apr 25, 2008)

I don't now what exactly remove carbon, but I did couple experiment before, I was added carbon in filter for 2 of 10g fully mature(more than 4 month from start) plant aquarium(wisteria, hornwort, crypt wendtii,some rotala, hygro,alternatera, taiwan moss), no co2, no fertilizing, substrat-top soil. In first tank I have carbon for 2 weeks, other one had more than month. In #1 plant's stop growing ( no bubbling, old leave's got hole's and start disappear )after 7-10 day of use and will need to restore ,after I removed carbon ,more than 10 week's , # 2 got all plant freeze forever(stop growing, slow desappear all plant, survive just moss( was looks thiner than usually but still healthy)), I guess plant's can restore but I throw away it after 3 month, so, from my expirience has a point to use carbon in filter (for planted aquarium) just if you need remove some medicine and no more than 3-5 day. I'm not a scientist and that's not a axiom, just small research which I done


----------



## davemonkey (Mar 29, 2008)

I was just flipping through some threads and thought I'd bring this back up...since the subject oftens pops up from time to time.

Since accurate test kits can get expensive, would it work to do a less-than-scientific-approach? Anyone with 2 same-size aquariums could do this. Set them up identically (substrate, plants, lights, water source, filters, ferts, CO2 or excel,... ) and add activated carbon to the filter of only one of them. Someone may already have two tanks nearly identical set up, all you'd have to do is even-out the species/plant mass so they are equal.
Let them both run for a month, fertilizing and lighting, etc... identically, and just look for any significant difference in plant growth/health between the carbon and non-carbon tank.

Incidentally, I've always had activated carbon in my filter (it comes packed in the HOB cartridge replacements) and I had even used Kent's carbon pellets as a biological filter bed in that HOB before I knew I didn't really need the bio filter bed. I've never bothered removing it, even refreshed it recently to clear up the tank after a re-scape. My plants seem healthy and flourishing, but I wonder how it might be if I did not have carbon in the filter. I'd love to do a side-by-side, but I don't have another tank.

Anyone care to run an eyeball-it test?

-Dave


----------



## hoppycalif (Apr 7, 2005)

That would be a good test to try, but like Dave, I only have one tank, so I can't do it. Just don't underestimate the difficulty involved in setting up two tanks that really are identical except for the one thing you want to test. To make this test mean a lot more you would run both tanks identically for at least a month, preferably longer. Then, add activated carbon to the filter for one tank only and run another month or two, looking for differences in plant growth, etc. After that, remove the carbon from the tank filter, and add carbon to the other tanks filter. Again watch for a month or two. If the non-carbon tank grew better the first time, the carbon tank should greatly improve when you remove the carbon, and the first non-carbon tank should go "bad" when you start adding carbon to its filter. 

If anyone here is in high school and wants a good science fair project, that will also help out a lot of people, this would be a good one. But, you should be experienced with planted tanks so you can actually keep two identical tanks both doing well.


----------

