mysterybox;388561 wrote: simple.......
unlike nitrates which mostly remain in the water column, phosphate does not. It becomes saturated in the live rock, algae, sand, etc. Water changes do little to remove phosphates, which is one reason why it takes such a long time to remove it when you start gfo as it continues to leach from the organic matter.
Not true. Although phosphates do bind with rocks and substrates not all of them were introduced there. Some and usually alot of them were introduced in fish food and most of the waste. I know you are a fan of copy and paste so here it is.
rganic phosphorus compounds, as well as orthophosphate, are so prevalent in biological systems that any natural food necessarily contains significant concentrations of phosphorus. Not only can organic material be taken up directly to provide carbon, nitrogen and phosphorus, it can be broken down by organisms and released as inorganic nutrients, such as orthophosphate, ammonia, nitrite and nitrate. The metabolic breakdown scheme for typical organic materials in phytoplankton1 is shown below:
<span style="font-family: Georgia">(CH</span><span style="font-family: Georgia">2</span><span style="font-family: Georgia">O)</span><span style="font-family: Georgia">106</span><span style="font-family: Georgia">(NH</span><span style="font-family: Georgia">3</span><span style="font-family: Georgia">)</span><span style="font-family: Georgia">16</span><span style="font-family: Georgia">(H</span><span style="font-family: Georgia">3</span><span style="font-family: Georgia">PO</span><span style="font-family: Georgia">4</span><span style="font-family: Georgia">) + 138 O</span><span style="font-family: Georgia">2</span><span style="font-family: Wingdings"><span style="font-family: Wingdings">à</span></span><span style="font-family: Georgia"> 106 CO</span><span style="font-family: Georgia">2</span><span style="font-family: Georgia"> + 122 H</span><span style="font-family: Georgia">2</span><span style="font-family: Georgia">O + 19 H+ + PO</span><span style="font-family: Georgia">4</span><span style="font-family: Georgia">---</span><span style="font-family: Georgia"> + 16 NO</span><span style="font-family: Georgia">3</span><span style="font-family: Georgia">-</span>
organic + oxygen <span style="font-family: Wingdings"><span style="font-family: Wingdings">à</span></span> carbon dioxide + water + hydrogen ion + phosphate + nitrate
Flake fish food is typically about 1% phosphorus (3% phosphate equivalent) by weight (and many products have such phosphorus data on their labels). Consequently, if five grams of flake food is added to a 100-gallon aquarium, 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 reefkeepers: what do we 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 heterotrophic organism consumes goes to provide energy, leaving a residue of CO2 (carbon dioxide), phosphate and a variety of nitrogen-containing compounds (ammonia, nitrite, nitrate, etc.) as shown above. A fish, whether it is an adult or a growing juvenile, consequently excretes much of the phosphorus that it takes in with its food as phosphate in its waste. Of course, overfeeding will result in more phosphate delivery than will reduced feeding levels.
Unfortunately, many types of seafood available at the grocery store have various inorganic phosphate salts intentionally added to them as preservatives. These foods include canned and frozen seafood, as evidenced by their label, and even some fresh seafood. In these cases, rinsing the food before using it may help to reduce the phosphate load it adds to the aquarium.
That being said it would seem to me that if those sources were removed by water changes before the phosphates were absorbed by the rock and other substrate their levels could decrease rather rapidly if the origin of the phosphates were removed before they were stored in the rock. I am assumming that the binding of the phospahtes is not instant and occurs over a period of time
If the rocks had been exposed to high levels of phosphates regardless of the source for a period of time then I agree with you blanket staement.
