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Originally Posted by straightrazorguy
I honestly don't understand why people use fozdown. Is it for extreme cases (after a period of neglect)? It's not a permanent solution, is it? That's what GFO is for. And if you're dealing with high phosphates why would you want to bring them down quickly? Don't corals hate sudden changes anyway? Can somebody explain this to me?
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No need to apologize and you asked some questions that other people are probably thinking about so I will do my best to answer them.
Yes, people use it in extreme situations. Several, including myself, have brought 200+ gallon tanks from 1.4mg/l of Phosphate down to 0.03mg/l with regular additions of Foz Down. As the Phosphate in the water drops the Phosphate in the rocks starts to be released. The Foz Down also neutralizes this. The situation of high Phosphate level in rocks is called Old Tank Syndrome.
It can be a permanent solution. That's how I use it.
Foz Down is a good replacement for GFO. Foz Down can reduce Phosphate levels to undetectable levels. Literature says 0.0015mg/l Phosphate. Since we need a little Phosphate in our systems Foz Down by itself is easily capable of doing what we need.
The instructions on the bottle say not to lower the Phosphate level more than .25mg/l in 24hrs.
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Originally Posted by straightrazorguy
OK, so what does this chloride salt do to phosphates?
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I used chloride salt as an example. Foz Down is a chloride salt just like the Calcium we add to our tanks to keep the Ca levels up. Both are chloride salts.
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Originally Posted by Proteus
Though I'm not sure if the bound phosphate will break down and source back into water column. I have used filters socks and skimmer to remove the particles. Also being bare bottom tank I syphon out detritus along with bound phosphate
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To my knowledge there is no studies about whether it will ever release the Phosphate back into the system.
If we consider that Calcium chloride reacts with Alk in a similar way to Foz Down reacting with Phosphate ie flocs. Then since we know that once the calcium carbonate is formed(by the snowstorm(flocs) in the tank caused by Calcium chloride and Sodium bicarbonate) it doesn't dissolve unless your pH goes below 6.9(ie Calcium reactor pH). If the pH of your Display tank is lower than 6.9 your tank is on it's way out. Since Foz Down can be used on ponds as well as freshwater tanks which have a pH around 6.0 to 7.5 and it still works well. My belief from experience is that it will not release the phosphate if pH is above say 5. It may however never release the phosphate at all. No one knows whether it will or will not. Since our tanks are all over a pH of 5 I think the concern about releasing Phosphate back into the water column may be a false alarm from lack of scientific studies.
Another point I would like to make about Granular Ferric Oxide is that it is Iron based. I suspect that when you put it into your tank it releases Iron into the water? The HC-GFO I used to use went from orange/brown to black. We know that Iron fuels the growth of macro algae. Does anyone know if there is studies about whether GFO releases Iron into tanks and if the Iron released causes macro algae blooms?
Cheers,
Tim