[MitchM]

Randy did an article a couple of years ago on phosphate, and here are a few paragraphs:

Phosphate Sources in Reef Tanks

Organic phosphorus compounds, as well as orthophosphate, are so prevalent that any natural food will contain significant concentrations of phosphorus. Flake fish food is typically about 1% phosphorus (3% phosphate equivalent) by weight. Consequently, if 5 grams of flake food is added to a 100 gallon tank, there is the potential for the inorganic orthophosphate level to be raised by 0.4 ppm in that SINGLE FEEDING. That fact can be a significant issue for reef keepers: what to do with all of that phosphorus?

If the food is completely converted into tissue mass then there will be no excess phosphate. But much of the food that any organism consumes goes to provide energy, leaving a residue of CO2, phosphate, and a variety of nitrogen-containing compounds. A fish, whether it is an adult or a growing juvenile will consequently excrete much of the phosphorus that it takes in with food as phosphate in its waste. Of course, overfeeding will result in more delivery of phosphate than will lower feeding levels.

For those interested in knowing how much phosphorus is being exported by macroalgae, this free pdf article in the journal Marine Biology has some important information. It gives the phosphorus and nitrogen content for 9 different species of macroalgae, including many that reefkeepers maintain. For example, Caulerpa racemosa collected off Hawaii contains about 0.08 % by dry weight phosphorus and 5.6% nitrogen. If one were to harvest 10 grams (dry weight) of this macroalgae from a tank, it would be the equivalent of removing 24 mg of phosphate. That amount is the equivalent of reducing the phosphate concentration from 0.2 ppm to 0.1 ppm in a 67 gallon tank. All of the other species tested gave similar results (plus or minus a factor of 2). Interestingly, using nitrogen data in the same paper, it would also be equivalent to reducing the nitrate content by 2.5 grams, or 10 ppm in that same tank.

The entire article is here:
http://advancedaquarist.com/issues/sept2002/chem.htm

So how are you exporting YOUR phosphates?


Mitch