Pink spots on rock

[Iodizedfate]

Okay here's the details.
Just set up a 20 gallon long 2 weeks ago. Have 2 OC clowns in it. Running an aquatech 30-60 hob with pillow floss.
Today I noticed pink spots in my rocks. Only outside introduction to the tank was about a 1/4 cup of sand from a friends tank to help cycle the rocks (fishless, in a bucket for almost 2 months, amm, trites read zero before fish).

I also used about half a gallon of sand from another tank that I rinsed pretty good but still ended up getting some ammonia reading off of it for a couple days until the bacteria took care of it.

What could it be?

Here are the stats:
Temp: 80
Salinity: 1.0245ish
Ammonia: 0
Nitrite: didn't test (it was 0 a couple days ago)
Nitrate: 20 ppm
Phosphates: 0.25 (from a couple days ago)

Here's a picture

 

[fishybuisness]

It could be coralline algae


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[Iodizedfate]

Yeah, I don't know how it could be though. The only the I put in it from any active tank was the 1/4 cup of sand. And my buddy's tank, while it has some, isn't exactly swimming with it. I mean anything is possible, I just don't feel that it's likely.


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[fishybuisness]

It's most likely either coralline (good) or cyano (bad) keep an eye on it and keep us posted


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[PB_Smith]

My vote is for cyano

 

[Iodizedfate]

Talked to a friend of mine and he said it was old dead coralline from when the rocks were used previously. The spots might have been bleached out and regained color when put back in salt water.