Refield Ratios - Practical Application

Most of us have heard of the Redfield ratio, which states that marine plankton contain 116 atoms carbon to 16 atoms nitrogen to 1 atom phosphorous. This is a slightly variable, but otherwise stabile analysis of marine organic carbon-based life. You can read much more about it in the internet.

In the last couple of months I had decided to re-make my reef, which was over 13 years intact. In the process, which is still on-going, I moved the main organisms to a smaller tank while I redecorated. The resut was a general collapse of this smaller tank, partially due to the old live rock, partially due to overcrowding. Be as it may, the PO4 levels started to rise. As I use Vertex Pro-Bio pellets for my carbon dosing, the NO3 level was literally at 0. This exponentially growing change seemd like a good chance to monitor changes based on the Redfield Ratio.

As carbon was not an issue, I started dosing CaNO3 when the PO4 reached over 0.3, which is the highest my kit registers. The actual level could have been as high as 1.0ppm, but I didn't attempt to read in this range. The levels were critical enough.

I made a solution of CaNO3, calcium nitrate, which is a simple fertilizer found in garden centres. In theory, one could use ammonium or another nitrate as a source, such as sodium nitrate. The actual concentration of the solution was not perfectly calculated, as I knew more or less what I wanted, which is about 100g in 500ml, a strong solution. I added this in small amounts over a 24 hour period to bring the NO3 level to 5ppm, which is the top of my testing range. I tested after each dosis to make sure I didn't overshoot my goal.

After two days the NO3 level has dropped very little, about 1ppm, but the PO3 has dropped to 0.15, about a 50% reduction! Clearly a positive result.

Many have used this method to balance their nutrient levels, but most haven't given any simple, practical guidelines with expected results. I hope to underline the ease of this kind of dosing to bring the PO4 level under control when dosing with a carbon source, particularly a solid source (bio-pellets), which tends to favour the assimilation of nitrogen vs phosphorous. Although the mixing of a specific NO3 solution should remain consistent, the actual concentration is less important than the application and dosing regimen.

Divers really get to see what we cannot keep!  Jealous, well, sometimes.  Just looking at a few shots one sees what an amazing diversity of life forms live door to door, stretching out into each others space, co-existing, fighting or otherwise just carrying on.  A very sobering experience, putting our feet back onto the ground.

Here are a few shots from my dear friends Marion Muck and Dietmar Günther.

 This little guy is smaller than the nail on your little finger!  The small sponges make a good comparison.

This is definitely a strange friendship.  The clarity of this shot is amazing!

He is a bit larger than your thumbnail, H. deniseae.  Various colour forms are know ranging from deep red to pale gold.

A shot of the adventurous couple. All fotos used with permission.  For information or use of their wonderful fotos, please contact them through www.pearlfisher.de

Filter Sox...or is that Socks

I think the Americans were the first to really make use of filter sox, and thus I will use their spelling for the plural.  These usefull, if somewhat confusing to many, accessoires, can be extremely helpfull.  Others, find them a nuisance.

Why use them?  What do they do?  Aren't they just another gimmik?  A waste of money?  Guy and Gals, this depends solely on you!  As most items in the marine aquarium, they are a tool.  You either choose to use it or not.

A brief description: essentially a tubular filter fabric mounted either on a hard plastic ring or hemmed with a draw-string closure.  There are various porosities, such as 100micron, 200micron, 300micron, etc.  This refers to the particle size that gets through.  There are two general material types; nylon and polypropelene mesh fabric.  The nylon is a fine, thin weave, while the PP is a sponge-like material.  They catch the particles in slightly different manners, with the nylon simply not letting the particle through, while the PP captures the particles in its mesh-like material.

Are there advantages to one over the other? Depends on what you want.  I hear very often complaints such as,"'I have to change out my sox every 3 days" or "it is so difficult to rinse the poly sox".  OK, let's get real, here, isn't the sock doing what it should?  Removing the fines!  Of course you will need to rinse or change it out often.  That is the idea!  If this is not your cup of tea, then don't use them.  A requirement they are not, they are a refinement.


The use of such a tool should seem pretty clear: it captures fines (and not so fines, such as alga and food) out of the water column before they get into the sump.  The idea is, by regularly rinsing and/or changing out the sock, you are removing potential NO3, PO4-forming and other non-dissolved wastes before they are broken down and more difficult to remove.  In other words, it will keep your water crystal clear and help reduce the production of DOC (dissolved organic carbon).  IF YOU MAINTAIN THEM.  If you do not regularly rinse/wash and replace them, they simply create a nice place for the materials to breakdown into DOC.

If you have a FOWLR set-up, instead of a reef, then they are a true blessing.  These tanks tend to produce a lot of detritus and sox help keep the water clear.  If you have a reef, especially a pro-biotic set-up, they may be less interesting, depending on your aesthetic.  Yes, they will filter out potential food for filter feeders.  On the other hand, mine have lots of pods and gamarus living in them, which I pour into the tank when I change them out.  A plus and minus effect. Here the PP mesh-type is best as it really holds the particles.

Are they worth it.  Like I said, you are either the sock-typus or not, but they do capture an extremely large amount of waste, which leads me to continue using them.  And I change them out every 3 days.  For the record, I prefer the poly mesh-type material, as the nylon is, in my opinion, too fine for a reef tank.

Cleaning!  How does one go about this? Really quite easy, but, as with anything wet, can get messy!  The nylon sox can be simply rinsed under warm water, easiest in-side-out, and occaisionally put through the washing machine.  Essentially the same with the PP models, but they capture more material and are best rinsed to remove the bulk and thrown in the machine.  The hot wash with a bit of bleach is fine.  No detergent is necessary, but, if you must, just a small amount.  After going through the machine they should be rinsed with clear water to remove any residues. I have 4 sox at hand, three of which are typically waiting for a wash.  I do them seperately from my house laundry and do not spim them.  They last me about 6-8 months.

There is a draw-string model of filter sock that can be used for a variets of other items.  In areas of the sump that produce bubbles, they are a great way to keep them under control.  Tie them to the skimmer exhaust, extra drain pipes.  Also for carbon as a three day cure (nylon best, here), direct at the overflow.

The decision is easy to give them a try.  Most like the results, some just let them get dirty and fall under their own weight.  Like I said, a tool.  Some of us are better with a hammer than others......

Fotos coutesey of Vertex Aquaristik GmbH

Understanding RGB in LEDs - Mythbusting

I've posted this on a few forums, but think this is an important subject that requires some explaination.  Enjoy.

With all the hype going on with RGB (red, green, blue) LED combinations, I wanted to take a moment and explain some of the mythology associated with this approach. I know we are all fascinated by a potential magic bullit.

First, we need to understand what light is and what light LEDs produce. Most of us know that visible light is but a splinter of the electromagnetic spectrum, which includes wavelengths such as infra red (heat) to gamma radiation (destroys living tissues). LEDs are a technology that can produce very specific radiation wavelengths. We are familiar with the current favourites such as Royal Blue (450nm), Blue (470nm) and Cool White (a phosphor LED with a mixed spectrum peaking elatively low in the yellow-green and high in the royal blue). These are all within the photosynthetic spectrum, often called PAR (photosynthetic active radiation). This is essentially visible light. Depending on the organism, various parts of this spectrum are utilized for their photosynthesis. This is an evolutionary adaptation which allow the organism to thrive in its given environments. Needless to say, the actual parts of the PAR spectrum utilized can vary greatly. Land plants utilize most of the red to far red spectrum, as well as the blue to UV spectrum. Sea plants, such as zooxanthellate alga, use mainly the blue spectrum, as this is most abundant in shallow seas. The red is simply filtered out in the first few meters of water and thus not available for photosynthesis.

Now, this demarcates the area of useful radiations for any given environment, which we often refer to as PUR (photosynthetic utilized radiation). For our marine aquariums, this embraces the spectrum from about 530nm down to 380nm, of which most of the PUR is between 400nm-500nm with strong peaks at about 410nm and 450nm, give or take a little. This makes radiations outside of this spectrum less interesting for our corals and most other creatures found on the average reef, which is typically 10m deep or more (the exception being tidal reef tops, of course).

Now, with this base information in mind, let us look at RGB lighting. We can simply say we have radiations at 470nm (blue), 530nm (green) and 630nm (red) from the get go. Of these, the blue is the most usefull for corals, although it peaks a bit high. Many animals do use this spectrum and it does enhance many fluorescent pigments. A definite win for the aquarium. The green radiation comes on the border of usefull radiation. For photosynthesis, it is largely useless, but for the production of certain pigments or at least their fluorescence, it is usefull. On the other side of the coin, it starts the range of cynanobacteria PUR, which then runs up into the yellow. It is a radiation to enjoy in smaller amounts and with some caveats. Now, the red, at 630nm, is at the start of the classic land PUR for very shallow water life forms. It will encourage certain alga, but, interestingly enough, will actually restrict the populations of zooxanthellae in a coral! (this may be guild related). An interesting quality. In very large amounts, it could potentially damage or even kill a coral via bleaching, while in controlled amounts will aid in modeling the colour of corals via this zooxanthellae restriction. It is an area that needs to be better researched. (new research was published April, 2015. See http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0092781 for this research)

OK, this all sounds fascinating, but what about all the cool colour blends one can create with an RGB set-up? Yes, with these colours one can visually mix any given colour (within reason, as colour is a bit more complex) for their aquarium. Our eyes will be quite happy with the results. However, to attain the humanly aesthetic results, we are tricking ourselves into believeing that our corals are getting what we see. Let me explain.

Our eyes will mix received radiation and create colours that are radiation-wise not there. For a simple example, a combination of red and blue light will appear violet to our eyes. This is not violet radiation! If we analyze the spectrum, we will find that it is still a combination of 450nm and 630nm, not a true violet at 420nm! The same is true for any visual colour effect mixed via this method. It is the same thing we see in printed material, where we are using cyan, yellow and magenta with black to create the entire rainbow. Our eyes are tricking us into see what we have lead them to see. Actually, a very cool thing, as, without this, colour printing would be close to impossible. Many will remember from school that the cones in our eyes detect specific groups of radiation with preference, creating what we call trichomatic vision. The cone receptors of our retina interpret blue-violet, green and yellow-orange (red) wavelengths into the complete rainbow or possible colours. Of course, our corals do not see the world through our eyes and, with a RGB spectrum are missing much of the vital radiation they need to fill their PUR spectrum. The bottom line is: if the radiations are not produced by the light source, it is simply not there! Regardless of what our eyes are trying to relate to us.

This is not to say that RGB is a bad thing, simply that one must understand what one actually has. As a supplement to a good PUR spectrum, it does allow the aquarist more scope in mixing the aesthetic. It does not substitue for missing parts of the electromagnetic spectrum.

If you have questions, do ask. Many of the obvious questions can be better answered with a Google search, where you will find in-depth discussions of human vision and the visible spectrum, as well as PUR and PAR.

Bio-Pellets-Update 2

As I've been busy with the rest of life, the time has been quickly eaten-up, but a few more thoughts on bio-pellets are due.

I mentioned in the last up-date, the PO4 level was slowly rising, while the NO3 was stabile at about 0.25ppm, which is extremely low.  These readings were taken with the new Red Sea test kits, which I have been playing with and do seem to be accurate.  In short, over the last 3 weeks the PO4 has risen to about 0.3ppm, which is extremely high for ULNS (actually right out the top!).  Although I had suspected my skimmer may have been less than efficient, I have taken time to re-clean it and play with its setting to maximize efficiency and am satisfied it is doing its job.  Then why the strong rise in PO4.  Well, it would seem we have a classic example of nitrogen limitation, which is throwing the Redfield ratios through the grinder.  With only a scant amount of nitrogen available, the bacteria are unable to assimilate the PO4 efficiently.  We have been supplementing carbon via the pellets, and they are doing a fab job of reducing the nutrients, but, at some point, if there is not enough nitrogen available for PO4 reduction,  the levels will simply rise.  Solution: add nitrogen to system.

I have started adding enough ammonia to the tank to raise the levels of NO3 to 4ppm.  Testing the water after 2 days showed that the NO3 had reduced to 2ppm and the PO4 was down to less than 0.2ppm, which seems to show that this is working.  The next reading (24 hours later) was a PO4 of 0.15 and the NO3 has dropped to 1ppm or a bit less.  I will continue dosing the ammonia and see how low I can get the PO4.

What I had found interesting during this PO4 rise, with the extremely low NO3 was, the corals did not brown out.  Rather a few became lighter, which leads me to believe that the NO3 is the main food for the zooxanthellae, not the PO4.  On the other hand, polyp extension became less and finally stopped altogether as the PO4 rose.  Also, growth slowed considerably, especially in the acroporas.  It would seem clear that the PO4 is interupting certain processes.  It has been documented that phosphorus ions will be built into the aragonite matrix of coral sleletons, should it be in overabundance, to the detriment of the structure.  It has been mentioned in research that the phosphorus ions prohibit the addition of Ca+ and Mg+ to the structure, causing a slow down, possibly impass, in the construction of the skeleton.

Bio-pellets: Update

Since the Vertex Biopellets have been used, I have gone from a relatively high PO4 down to an almost unreadable level and, currently, about 2 weeks after the extremely low reading, the PO4 has been creeping up again.  I'm not really sure why, but I get the feeling that my skimmer may not be efficient enough to rermove the bacteria waste in the amount that it is produced.  Otherwise, why would the PO4 rise in a 'nulled' system?  There have been no changes in feeding or inhabitants, no dead creatures, etc.  It would seem that, after the bacterial bloom that reduced the PO4, the skimmer is not removing all the bacteria and it is dying and the contained phosphates are being released back into the water column.

Next step, a new skimmer.  I have been planning on testing the Vertex cone skimmer, but need to redo the sump first.  Hopefully this will all happen in the next weeks, as I am also waiting for a new stand for the refugium part of the system.

I can't say that the corals appear to be suffering.  It is almost as if the biopellets do have an additional effect, which benefits the corals.  I had noticed a similar general improvement when I first started working with Zeovit.

The Carbon Cycle - Part 2

What is particularly interesting for us about the Redfield Ratio is that it gives us a clue as to how to control waste build-up in our aquariums.  Our aquariums are not a natural environment, however, the inhabitants will still follow the same rules as on a living reef.  We can be assured that the Redfield Ratio will still impact the system.  In the end, the chemistry doesn't change.

What does change is the unnatural amount of nutrient we add to our aquariums.  As on the reef, the nutrients reach a state of breakdown of ammonias and phosphates.  On the reef we find plenty of bacteria that will assimilate these wastes and remove them from the water column.  These wastes are not actually gone, they have simply changed their state by being incorporated into another life form.  Plankton!  Bacterial, plant and animal.  As we know, plankton is, also, a food source for many creatures.  Clams and other molluscs filter it from the water, as do sponges, tunicates, various worms, etc.  In an aquarium we rarely have enough of these filtering life forms to compensate for the wastes of our larger , non-filtering life forms, should we manage to produce enough waste product assimlating bacteria.

Going back a step to the bacterial plankton, we have learned that its production follows the Redfield Ratio, 16C : 16N : 1P.  In a typical aquarium, the wasteproducts containing nitrogen (ammonias:NH3, nitrates:NO3, nitrites:NO2) and those containing phosphorus (phosphate: PO4) are more common than carbon.  The aquarium becomes carbon limited and the levels of these waste products rises.  Without sufficient carbon, they cannot be converted into (bacterial) plankton.  Conversely, one may have sufficient carbon present from carbon dosing, but not enough nitrogen, which leads to a rise of phosphate,a common scenario in older tanks during changeover to a probiotic system.  One can, also, have a phosphate limitation, which will lead to the nitrogenous waste level rising.  Balance is the thing.

In an effort to maximise this cycle, we add a source of carbon to the aquarium water.  First experiments were made with alcohol, sugars and acetic acid (vinegar), amongst other chemicals.  This is based on a long used technology to treat waste water in water treatmant facilities.  It is really nothing new, simply the application is new.

Suffice it to say, these methods work.  Some a bit better than others, but, as each aquarium is a bit different, one cannot expect identical results.  What is clear is that pushing the Redfield Ratio reaction reduces nutrient waste levels in closed aquarium systems.  We don't know all the complex chemistry that lies behind this nutrient reduction, as this is not a simple path, rather a complex network of possible reactions that lead, via bacterial guilds, to this reduction.

Now, one of the first things one will notice, if they pour a capfull of vodka into a nutrient laden aquarium, is the aquarium water clouds overnight.  Often accompanied by the death of many, if not all, of the higher life forms.  Shock of shocks!  Well, one does learn from this, as it doesn't have to happen this way.

What has happened is that enough carbon has been made available for a massive bacterial bloom in this closed system.  In and of itself not bad, but, quickly reproducing bacteria take the oxygen out of the water so rapidly, that the higher life forms asphyxiate from lack of this life giving gas.  This is why one starts slowly to convert a standing aquarium to a probiotic system.

As I mentioned above, it is a rare aquarium that has enough filterfeeding organisms to remove the produced bacterial plankton.  This removal is mechanically done via a protien skimmer.  But that is another subject.