cooking live rock
 

I have about 80lbs of live rock that I have been cooking in a tub for over four months now and I am still getting high phosphate readings. I am getting almost no detritus in the tub when I do water changes. When I swish the rocks in a bucket the water ends up tinted green which is the colour of the dieing/dead coraline. What I am wondering is if this could be the source of the phosphates. If I had a light on the tub and the coraline started coming back, would the phosphates stop showing up?

All the reading I have done says to keep cooking until the phosphates stop, but they also usually suggest that it will be done in about three months or shortly after the detritus stops coming out. Does anyone have any firsthand experience that relates?

I did this and it worked well. Reduced the phosphates very quickly, and the tank is now set up with zero phosphates.

That is interesting, I hadn't thought of using carbon dosing to speed it up. I guess the only question is how do you really know when the rock has been depleted of phosphates when you can't test for it in the water due to the bacteria consuming it. I guess it doesn't matter if you keep some type of carbon dosing going after the tank is setup.

I was thinking of trying to find some lanthinum chloride to use every couple days to drop the level in the water back to 0 after it has climbed. I find mine is climbing to about 1ppm in 3-4 days and staying there until the next water change. I could do a lot more water changes as well but that is a lot more work and money. I'm just not sure where to get lanthinum chloride.

But I'm really wondering if my rock actually has phosphates left in it or if the phosphate is just coming from the coraline die off. If it is just from the coraline then I should be fine onece there is light on it.

When the carbon source is used up the skimmer will slow down to almost nothing. Wait a week and test for phosphate. You want it to be below 0.1 before you use it in a tank. GFO and time will take care of the rest.

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Well I think I will give this a try in a few days. I did my water change and am just waiting for the phosphates to build back up a bit. Strange thing is I had a fair amount of detritus this time where there has been none the last four weeks. It looks like the green coralline is finally disappearing as well. Hopefully this means it is getting close, I am getting impatient.

Is there a light source near the tub, or does it have a closed lid?

No light. It is in a room with no windows in the basement. It has a lid but it doesn't cover the entire top because it has changed shape from the weight of the water.

You could do a few big big water changes. When i cooked all my rock for my 125 I waited for it all to cycle and then the p04 was really high I did a 100% WC on the rock and washed it off quick in the old water put it in new water added a bag go GFO close to the Power head and next week tested again and P04 was gone

For the most part the phosphate is in the water not the rocks

I do weekly 100% water changes. By the end of the week I'm reading at least 1ppm. I'm not running gfo though.