What happens to DOCs?

[PIPSTER]

Everyone preaches how bad DOCs are, but what happens to them?

Do they eventually break down into ammonia to be removed by the nitrogen cycle?

Do they stay "forever" in the water column, accumulating to toxic levels?

Skimmers only remove approx 20% of DOC, but for those who don't do water changes, like GlennF for 11+ years, that means 80% of DOCs were never removed.
But his reef is thriving. He carbon doses and skims, but that's not removing all DOCs, it's just helping handle nitrates.

But my tank handles nitrates all by itself just fine. 0.03 ppm NO3.

Can't a combination of coral, CUC, critters like worms and pods, and the rest of the food chain keep a tank going, as long as the bioload isn't overwhelming, perpetually as far as taking care of toxicities?

Then we just need to dose appropriate alk, calc, mag, and traces, and of course feed the livestock.

Why not?:hammer:

 

[PIPSTER]

Nobody knows?

 

[Fish Everywhere]

As far as I know, Dissolved Organic Compounds (DOCs) in the water can be removed by multiple methods aside from skimming. Skimming removes, as you said, 20-30% of DOCs from the water. The remaining amounts are removed by running carbon, doing water changes, and coral consumption.

This mimics my experiences and many others. Aside from good tank husbandry and not skimping on equipment, you shouldn't really have to worry about DOCs becoming a major problem provided you skim well and replace carbon every 2 weeks.

 

[Timfish]

Algae and corals (as well as other life forms) release DOC (Dissolved Organic Carbon) into the water. Testing for DOC is not possible at the hobbyest level yet* My understanding DOC can be catagorized as "Labile" (easily metabolized by some organisms), Semi-refractory (can be metabolized by some organisms under certain conditions), and Refractory or Recalcitrant (very difficult to metabolize), this last form makes up roughly 2/3s of the DOC in the ocean (1).

DOC released by folacious (nuisance) algae promotes heterotrophic or oxygen reducing microbes. (2)

DOC released by corals promotes autotrophic or oxygen enriching microbes(2)

Many cryptic sponges (found on wild or maricultured live rock only) feed off DOC and convert it into DIC (Dissolved Inorganic Carbon)(1), much of which is in the form of bicarbonates benefiting corals.

I would strongly recommend Forest Rohwer's "Coral Reefs in the Microbial Seas" as a starting point (Kindle version is about $10). There is a ton of research out there but two researchers to start with would be J. M. de Goeij and Andreas Hass.


* Researchers at the Steinhart Aquarium have used 235nm(?) UV light to measure TOC relatively reliably. It seems to me this could be developed into a tester much like the digital testers available for other parameters but I have not heard of any further development.

(1) http://www.rug.nl/research/portal/files/14555035/13completethesis.pdf

(2) http://www.ncbi.nlm.nih.gov/pubmed/23882445

 

[Reef Frog]

Nitrogenous compounds are released into the atmosphere as pure nitrogen gas eventually in a ideal well functioning bacterial filter.

It and phosphates is also recycled into algae, phytoplankton and animal tissues. It's sequestered in animal & plant tissue and the organisms & mulm on rock and in the sand bed.

Other compounds mineralize and can hang around with little bio effect.

Amount of food and feeding frequency are a big factor in build up levels. I can see how a growing coral tank top with clams & filter feeders with no to minimal fish load (therefore minimal feeding) can seem like a semi self sustaining closed system for a long period of time. But it's not.

As stated filter socks, many media & bacterial processes export it. Siphoning detritus removes a great deal. Much DOC finds its way into the sand bed where it can lie in wait in an anerobic encironment.

Keep in mind that over accumulation of detritus can take years with few negative symptoms and then one day many years later someone somewhere reports a tank crash due to OTS (old tank syndrome) aka LARS. They just passed a point of no return. Anybody who's taken apart an old, fed mature aquarium knows what I'm talking about.

In the end, organics must get sequestered or removed somehow in a closed aquatic system, or perhaps never introduced in the first place. Each tank is completely different & unique in this regard.

INTERESTING TIDBIT. The side of my Salifert test kits lists "Orgsnic Pollution" as a test kit they offer for sale. Never seen it and don't see it advertised, or know how/ if it works(ed). Anybody know what this was about? Of course the yellow water test in a white bucket is a decent eye ball measure of your waters richness.

 

[photoblepharon]

Researchers at the Steinhart Aquarium have used 235nm(?) UV light to measure TOC relatively reliably. It seems to me this could be developed into a tester much like the digital testers available for other parameters but I have not heard of any further development.

254nm.

It's a spectrophotometer reading that requires no reagent so it's not inconceivable that it could be made much cheaper for hobbyists, some day. The test is very simple and basically requires putting the water in and pushing a button.