Rock growth Changes Color Through Day

[Heathcliff37]

Hello,

I recently got a small piece of rubble from my LFS to seed my dry rock. On it are little spots that are pale during the night, but after an hour in the light turn brown. I've included pictures and circled the spots in question.

The craziest fact is that they can move locations! I've seen them move onto the white sponge on the front, which is when I first noticed they were actually shifting locations.
What could these be?

 

[T-J]

The pics where they are brown look like Dinos.

 

[Heathcliff37]

The pics where they are brown look like Dinos.

I dont know , they seem a little big to be Dinos.

 

[thatmanMIKEson]

Do you have a diatom issue?

 

[T-J]

I dont know , they seem a little big to be Dinos.

Not at all. For the first time in my 25 years of keeping SW, I had dinos in my latest tank. Here's a pic of when they started. They can get quite big, and are a pain to get rid of.

 

[Heathcliff37]

Do you have a diatom issue?

I wouldn't call it an "issue", but I do have a lot of diatoms. At least, I suspect they are diatoms, but I haven't checked under the microscope yet.

 

[Heathcliff37]

Not at all. For the first time in my 25 years of keeping SW, I had dinos in my latest tank. Here's a pic of when they started. They can get quite big, and are a pain to get rid of.

I meant that individual dinos themselves would be too small, but it is true clumps of them, such as is in your picture, can get larger. I assumed my mystery organisms where individual units, just based on how they move, but it's possible they aren't.

 

[Heathcliff37]

Not at all. For the first time in my 25 years of keeping SW, I had dinos in my latest tank. Here's a pic of when they started. They can get quite big, and are a pain to get rid of.

Did yours change color after being exposed to light?

 

[thatmanMIKEson]

Not at all. For the first time in my 25 years of keeping SW, I had dinos in my latest tank. Here's a pic of when they started. They can get quite big, and are a pain to get rid of.

That looks like chrysophytes...

 

[Heathcliff37]

Well I guess it will remain a mystery for now!

 

[Bribo12]

They look like barnacles to me.

 

[madmarks]

They look like barnacles to me.

I am leaning along the same lines. It appears that the 'brown' phase is arms extended feeding or them being open. They resemble an acorn barnacle. The bottom row is isolated from your pictures. See if the close up when a shadow passes overhead.

 

[Heathcliff37]

I am leaning along the same lines. It appears that the 'brown' phase is arms extended feeding or them being open. They resemble an acorn barnacle. The bottom row is isolated from your pictures. See if the close up when a shadow passes overhead.

This is very thorough response wow thank you! Barnacles seem reasonable, although I saw them move locations and barnacles are sessile. Maybe the moving organisms were something different that coincidentally looked similar? Anyway whatever they are I'm not concerned.

 

[madmarks]

This is very thorough response wow thank you! Barnacles seem reasonable, although I saw them move locations and barnacles are sessile. Maybe the moving organisms were something different that coincidentally looked similar? Anyway whatever they are I'm not concerned.

If you saw them move then they are not barnacles. The only barnacle that has been observed moving is Chelonibia testudinaria, the barnacle on sea turtles. They migrate to the position of best flow on the turtle's shell.