GFO and carbon...necessary?

[airtime23]

I hear people saying things about GFO depleting elements other than phosphates and that one shouldn't add a lot of GFO at once because their corals might suffer? Why? What else does GFO remove that corals need (other than phosphates)?

How about carbon? I've heard people say that their corals look bad after they added carbon...so why do people use it? Has anyone done an A-B comparison on their tank? Run carbon for a while and then go without it to see how their corals reacted?

I'm interested to get some opinions on this and to see if there is any definitive data that says that one should definitely use one or both on a mixed reef tank.

Thanks in advance.

[DaveRaz]

Both serve a purpose for me. I run the carbon reactor 2 or 3 days per month to help polish the water. I run the GFO when my P04 is .04 or higher. I have learned the hard way buy losing some coral early on that stability is key. Not really chacon get numbers but trying to find your tanks sweet spot and keeping it there is the challenge.

[laga77]

I don`t believe it is the GFO Or carbon causing the problems with the corals.

[Ted_C]

Carbon and GFO reactor outputs should always be directed to a filter sock - and a good filter sock at that - like 25 microns. Those problems you hear about can almost always be attributed to the lack of filtering the output.

The "fines" can easily go through the sponges on the reactors - causing problems for fish (i.e. tangs and HLLE) and corals alike.

The HLLE issues are well documented on here and other literature. I have no proof of the irritation of corals - so it's only a guess. The guess is based on - corals absorb whatever's in the water when they build their structure out. Little flakes of iron or alumunium or carbon that get embedded int hat structure can't be good.

As for the depletion of elements - GFO is supposed to take up alkalinity - but for the life of me - I couldn't tell you the chemical mechanism of what that might be. Maybe it's an affinity attraction rather than a chemical reaction - but I still don't see how a cup or two of GFO can affect the alkalinity that much.

I personally will not run GFO or Carbon again. While there are some success stories - there are just as many stories of success without these items.

[tmz]

GFO( granular ferric oxide ) adsorbs soluble reactive phosphate ( inorganic phosphate and some inorganic phosphate), silicate and some metals.
It is commonly used to lower organic phosphate to limit some types of algae and/or to prevent an alteration to the calcification process in calcifying organisms .
The later can occur when inorganic phosphate interferes with the formation of the skeletal matrix by stopping the growth of calcium carbonate crystals.
Overuse can lead to rapid drops in available phosphate or a phosphate deficiency which can harms corals , calms and others; they need some phosphate for a number of things like phospholipids, dna, phosphorylation, ATP etc.
Dust and fines may also irritate some animals.

Granualted activated carbon, GAC, mostly removes hydrophobic organics which hold some nutrients and other elements and perhaps more complex compounds including alelopahtic compounds .
Dusty types like lignite have been implicated in one study as a corntibutor to HHLE ( head and lateral line diesease) . About a year ago,one popular brand polluted and crashed an number of tanks due to metal contaminated .

There is no definitive genralizable data; a reef tank may do well without them or with them . They do specific things and can be useful tools when used correctly .

FIWIW:
I use rox8 gac in small amounts and have for many years. Very low dust, high porosity for aqueos use.

I haven't needed gfo in a about 18 months with the organic carbon dosing I do . Inorganic phosphate in the 0.02 to 0.04ppm range contributes to sustaining coral vibrancy and limited nuisance algae in my tanks.I prefer BRS high capacity gfo.; very low dust;sturdy and hold up without breaking up in a reactor.

[dkeller_nc]

As Tom stated, GFO and GAC are tools for use in water quality management. They're not required in the way that calcium and alkalinity supplementation are for folks keeping stony corals.

You could, for example, maintain a very low bio-load reef tank that has a continuous water-change system with a high enough water change rate that prevents the accumulation of organic pollutants such as yellowing compounds and soft-coral chemical warfare compounds. In such a scenario, using GAC might be unnecessary.

With respect to phosphate accumulation, one could run a water change system mentioned above (albeit at a much higher rate than necessary to prevent the accumulation of water-yellowing compounds) that would make GFO use unnecessary. One could also use carbon dosing and efficient, aggressive skimming to control phosphate accumulation as Tom outlines that would render GFO use unnecessary.

Like anything else in the hobby, encountering problems with GAC and GFO use is a matter of how much, how often, and the exact manner that it's used more than it is an inherent danger with their use. Suddenly running a boatload of GFO in a tank that has a relatively high water concentration of phosphate for a long period, especially without testing/monitoring the phosphate level with a an accurate test kit could result in real harm to the tank's coral population. But that's not an inherent problem with GFO, it's a problem with the way it's use is implemented.

One can come up with equivalent examples of harm that could occur with incautious implementation of GAC, kalkwasser, 2-part dosing, calcium reactors, biopellet reactors, and even coral foods.

[JamesWang]

New member, but I do have a bit of experience before the days of GFO and dosing!

No, nothing is required besides keeping the water clean and nutrient filled. Carbon, GFO, skimming, etc. are all means of doing this; but water changes can achieve the same.

I did run Carbon bags in my Wet-Dry (Old technology, in the days of car-phones and wind up ignitors) and had a huge benefit; clarity was improved, fish seemed healthier, etc. However to me this is just preventative maintenance, that is not required.

[tmz]

I do daily water changes ;1%. They help add and subtract elements and maintain constancy in element ratios. Skimmers also play a role in exporting amphipathic organics but also aid aeration significantly.

[ReefCowboy]

GFO or po4 absorbing medias are a must IMO. It's either that or algae. Some low quality GFO's aren't as efficient as some more advanced ones available today and thus need to be added in higher quantities to keep the po4 low over the course of a month or so when most of us replace them. Issue is a higher amount of GFO not only can cloud the water for a few hours which is unpleasant but can also promote a bit of a drop on alk levels.

I've never heard or read credible articles proving GFO absorbs other elements.

As far as carbon, I've read many threads before choosing some for my tank and noticed diff results with some types/brands. Carbon fine "dust" can cause HLLE but I think we should always strive for better brands, common to reefers to avoid or reduce risk of issues.

The reason people see paler corals with them is due to the fact that they add too much or too suddenly(I've done it myself).

In the search for the best one i ended up getting ROX.08 and that thing is scary powerful. It will def strip everything from the water over the first couple of days it's introduced.

It will help your tank look clear and some impurities under check.

[tmz]

I've never heard or read credible articles proving GFO absorbs other elements.

It does as noted earlier. There are plenty of things you can read if you search for them. The fact that it adsorbs some metals and silicate is not necessarily a bad thing;probably more helpful than not but something to know and account for. It may also have an effect on alkalinity but a relatively minor one.

Many tanks including mine do fine without it ; so, imo, it can be helpful but is not a must.

GAC even rox8 will not strip everything from the water. GAC takes out mostly organics that are hydrophobic(repelled by water) via van der Waals force not adsorbtion via covalent bonding or elctrostatic attraction as adsorbents do. It doesn't remove inorganic nutrients like phosphate and nitrate for example.

[bertoni]

This article covers some of the chemistry of GFO products:

http://reefkeeping.com/issues/2004-11/rhf/index.htm