Odd coloration on rock

[Westeri]

A little background info:

I purchased some reef saver dry rock (theoretically ancient sea bed that hasn't seen the ocean in a long time) and started "curing"/cycling the rock to create a bacterial colony.  I have been using shrimp pellets as the food for this task as well as some bacterial colony starter mix.  There is a flow pump in the bucket to cause water movement, and a lid on the bucket to keep out light (or at least drastically reduce it).

I noticed that the two buckets of my rock that started this process about two weeks ago are starting to show some pink coloration.  See pictures below:





My understanding is that coralline alga requires some sort of source and won't just appear on its own.  Is this just some sort of dye staining from the food?  Or possibly something else?

[chromiumlux]

There is a lot of controversy on the use of "mined dry rock". You may want to research this type of rock on the net. As this rock has been buried, for who knows how long, it would be wise to find out where it was mined from if possible. I have read a lot of disturbing articles on mined dry rock. Some of which indicated the leaching of heavy metals through the rock. I have also used this type of rock several times and I must attribute the use of this rock to my tank crashes and algae issues because I did not cure it properly before adding nutrients to the system. Plan to cure this rock for a long time to ensure sustainability.
I too, went the route of cost effectivness. I eventually went back to a quality live fiji rock and have had no issues other than a cyano bloom which has subsided.

This being my experience with dry rock in my tanks. Others may have had good luck with it.