Nutrient Export

SantaMonica

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What do all algae (and cyano too) need to survive? Nutrients. What are nutrients? Ammonia/ammonium, nitrite, nitrate, phosphate and urea are the major ones. Which ones cause most of the algae in your tank? These same ones. Why can't you just remove these nutrients and eliminate all the algae in your tank? Because these nutrients are the result of the animals you keep.

So how do your animals "make" these nutrients? Well a large part the nutrients come from pee (urea). Pee is very high in urea and ammonia, and these are a favorite food of algae and some bacteria. This is why your glass will always need cleaning; because the pee hits the glass before anything else, and algae on the glass consume the ammonia and urea immediately (using photosynthesis) and grow more. In the ocean and lakes, phytoplankton consume the ammonia and urea in open water, and seaweed consume it in shallow areas, but in a tank you don't have enough space or water volume for this, and, your other filters or animals often remove or kill the phytoplankton or seaweed anyway. So, the nutrients stay in your tank.

Then the ammonia/ammonium hits your rocks, and the periphyton on them consumes more ammonia and urea. Periphyton is both algae and animals, and is the reason your rocks change color after a few weeks. Then the ammonia goes inside the rock, or hits your sand, and bacteria there convert it into nitrite and nitrate. However, the nutrients are still in your tank.

Also let's not forget phosphate, which comes from solid organic food particles. When these particles are eaten by microbes and clean up crew, the organic phosphorus in them is converted into phosphate. However, the nutrients are still in your tank.

So whenever you have algae "problems", you simply have not exported enough nutrients compared to how much you have been feeding (note: live rock can absorb phosphate for up to a year, making it seem like there was never a problem. Then, there is a problem).

So just increase your nutrient exports. You could also reduce feeding, and this has the same effect, but it's certainly not fun when you want to feed your animals :)
 

Nano sapiens

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If I may, I can add a bit more to the nitrate picture.

Algae will grow when light, ammonia and/or nitrate, phosphate and iron are present. Algae can decline if any of these become limited.

Nitrification and denitrification processes occur in various locations in a properly maintained reef tank. When nitrification/denitrification proceeds efficiently and a tank is not overfed, nitrate buildup need not occur. 'Efficiently' is the key word and this is accomplished by regularly removing detritus from the tank to allow water to flow freely into the substratum to be processed by various aerobic/anaerobic bacteria.

When a tank is maintained in a balanced state, the many forms of phosphate are utilized by various organisms from coral down to bacteria. Bacteria and microscopic benthic algae in the substrate liberate small amounts of phosphate continuously which is then utilized by higher organisms and, if in slight excess, can be controlled via regular WCs. In properly maintained, balanced aquariums, old LR and LS need not 'fill up' with phosphate as can be evidenced by many tanks operating well with very old materials. The key is in keeping the phosphate input and export in balance.

Nutrient export can be accomplished via many different methods. My personal favorites are physical algae removal, aggressive detritus removal and regular WCs, but protein skimmers, algae scrubbers, macro algae refugiums and various phosphate removers can all work if applied properly.
 
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Timfish

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Starting with a quote by Charles Delbeek "Our crystal-clear aquaria do not come close to the nutrient loads that swirl around natural reefs" and "When I see the colors of some of these low nutrient tanks I can't help but be reminded of bleached coral reefs." Coral, Nov/Dec 2010, pg 127. It is important to maintain a balance between input and output. When we say "Algae will grow when light, ammonia and/or nitrate, phosphate and iron are present. Algae can decline if any of these become limited." it is critical to remember to include the Symbodinium spp dinoflagellate and cyanobacteria symbionts(1) corals are using when we are talking about reducing nutrients to reduce algae growth. Unfortunately many aquarists are starving or killing their corals by indescriminately removing all nitrate(2) and phosphate(3) because they do not understand these nutrients are essential for their corals health. Equally important is to remember the dinoflagellate symbionts are brown and while having too many can be a bad thing(4) brown coloration in a coral is a good thing and bright fluorescence can be an indicator of a problem(5)

(1) Discovery of symbiotic nitrogen-fixing cyanobacteria... [Science. 2004] - PubMed - NCBI
(2) http://wap.aslo.org/lo/toc/vol_48/issue_6/2266.pdf
(3) High phosphate uptake requirements of the scleractinian coral Stylophora pistillata
(4) http://www.nature.com/nclimate/journal/v3/n3/full/nclimate1711.html
(5) Stony Coral Fluorescence as a Measure of Health
 

Nano sapiens

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Looks like we've been reading the same articles :)

"Unfortunately many aquarists are starving or killing their corals by indescriminately removing all nitrate(2) and phosphate(3) because they do not understand these nutrients are essential for their corals health."

Very true. Old pervasive myths die hard and the 'corals just need sufficient light and extremely low nutrient water' is a hard one to eradicate since this statement shows up in so many older books, articles, etc. Understanding of the role that each partner plays (coral, zooanthellae, thraustochytrids, cyanobacteria, etc.) is now better understood, but we'll undoubtedly see some additional revelations in the years to come.


"Equally important is to remember the dinoflagellate symbionts are brown and while having too many can be a bad thing(4) brown coloration in a coral is a good thing and bright fluorescence can be an indicator of a problem(5)"

*Can* is the important word here. Using nature as a guide...

Having just spent a week in Palau, the various reef environments are still fresh in my mind. Beautiful extensive fields of healthy creamy-brown Acropora dominate the shallows, colorful Lobos and Favias the shallow, partially shaded areas and deeper water drop off zones. The current trend of very high intensity lighting in combination with unnatural, skewed light fields is one that is being scrutinized lately...and rightly so IMO.


Impacts of Nutrient Enrichment on Coral Reefs: Impacts of nutrient enrichment on coral reefs: new perspectives and implications for coastal management and reef survival
Symbiotic Thraustochytrids: Reefs Magazine - Thraustochytrids: The Most Important Coral Symbiont No One Knows About
 
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Kungpaoshizi

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note: live rock can absorb phosphate for up to a year

I thought I might add this is partially true. Calcium carbonate will absorb and leach phosphate continuously, until equilibrium is reached with the water.
Think of it like having GFO in your tank that sucks the phosphate out but pours it back in after it's "full" after the surrounding water has less than it does.
 
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SantaMonica

SantaMonica

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Yes but the starting nutrient status of a typical reef tank is rock=0 and water=high. So the first year or two is all flow into the rocks, which means the rocks are the main filter. Then they fill up and start the in/out equilibrium, otherwise known as old tank syndrome. Interestingly, most reefers think that their skimmer has been the "filter" all this time, and then wonder why things are getting worse.

This is of course, unless there is other strong export to keep the nutrients low in the water.
 

Nano sapiens

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My take: Rock and the sand bed (when present) are both involved in what we call 'filtration'. Some nutrient assimilation (periphyton, sponges, crustaceans,, etc.) and a whole lot of nutrient sequestering via flow advection. The sequestered material needs to be periodically removed for the system to function effectively. Tank maintenance should include blowing out of detritus accumulations in the rock (at least weekly), but sadly the implementation of this beneficial action is sometimes unknown, neglected or dismissed.
 

Salty1962

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My take: Rock and the sand bed (when present) are both involved in what we call 'filtration'. Some nutrient assimilation (periphyton, sponges, crustaceans,, etc.) and a whole lot of nutrient sequestering via flow advection. The sequestered material needs to be periodically removed for the system to function effectively. Tank maintenance should include blowing out of detritus accumulations in the rock (at least weekly), but sadly the implementation of this beneficial action is sometimes unknown, neglected or dismissed.
I blow my corals/lr and sand bed, not so much to create a dust storm and cause a whole number of other issues, weekly and with each wc. You'll be amazed at what settles on your corals and lr, I am:D
Great information everyone!
 
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