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