BTW, nice looking rock!!!
Calcium carbonate is a natural adsorber of phosphorus. If you have LR, you have introduced a form of P to your tank. Some rock will have more, some will have less. Luckily for us, bacteria are usually efficient enough to bind up most phosphorus before algaes can utilize it.
I can tell you why you are finding a lot of P in your rock and a lot of sediment.
This photo shows one of the areas that we use for the harvest of our Fiji Premium. The area shown on the left is about 40 kilometers in length and runs along the western side of the main Island. We are able to utilize this coast because of its heavy agricultural runoff and high nutrient content in the water. Very little coral grows on this coast because of the heavy wave action and large amounts of sediment and algae (including coralline) in the water.
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This picture shows a close up of the same area with some of the collectors working in the tidal zone. Interesting to note the average depth of the water that live rock is collected in and the lack of most other types of coral life.
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Once the rock arrives at the warehouse in Fiji it receives a thorough cleaning by our crew. First we clean off all of the excess plant life and sponge that will just decay in the shipping process then we power wash it to remove the mud. This step is very important to insure good clean rock during transit rather than stinky unclean rock that will really cause havoc on your system on the receiving end. This step also allows us to judge the rock for good coralline coverage and reject any pieces that do not meet the standards for Fiji Premium from Walt Smith International.
Once the rock is cleaned it is placed in our system and receives a constant spray of clean filtered water. We use spray to keep the coralline alive and moist while some of the "undesirables" either crawl off or (in the case of sponges) die off. Many people ask why we do not keep the rock fully submerged and the answer is simple. If we were to keep the rock under water at this stage of curing the ammonia created in the system would kill off everything, including coralline, and the stinky mess it would create would reduce the Fiji Premium to base rock. From our experience rock kept our way for at least 4 - 6 days prior to shipping allows for nice clean rock upon arrival without fouling your system.
http://pacificaquafarms.com/premium.htm
While I mostly have Marshall Island rock, I do have some Fiji mixed in because I really like the looks of it. However, IMO, any rock from Fiji should be cured well before adding it to the tank. There will be high P content due to agricultural runoff and there will be high sediment because they are digging it out of muddy areas and powerwashing it.
Does this mean, "Don't buy Fiji LR"?
NNNOOOO!!! It just means be aware that this LR comes from an area that has too much P for stony corals to grow because of agricultural runoff, contains a lot of algaes (including coralline), and is muddy. Curing well would be a very good idea IMO.
If you want to cure it with the lights on...fine. If you want to "cook" it with the lights off....fine. Each method has it's plusses and minusses. You will likely lose some of the coralline coverage with cooking but will have less adsorbed phosphorus and the pieces of broken LR that gets shed will be in a tub instead of your tank. You also won't likely have the typical "cycling" algaes in your tank.
If you cure it with the lights on, you will likely have to manually remove some problem algaes in the beginning, will likely have more diatoms in the beginning, more cyanobacteria in the beginning, etc. However, you will likely have more coralline algae and that is important to a lot of people.
I don't understand the "Us" vs "Them" on the issue. We all have differing goals for our tanks. Heck, I have 2 mantis tanks. Not many people find them as fascinating as I do. Those tanks are set up to cater to those animals. My attitude is let people do what they want. Let them know the facts about their choice but let them do what they want (as long as it isn't unethical).
I can personally testify that "cooking" doesn't kill everything. If you need me to upload a picture with my right hand raised and my left hand on a Bible, let me know. At the same time, while it hasn't happened to me, some people seem to have lost some of their coralline algae and that is a very big negative to some.
Pick your poison....neither method is without flaws. Choose which flaws you want to live with.