question for seasoned keepers

hey folks, I have this odd biofilm on my rocks that wont seem to go away. I rode it out for about 3 weeks so far thinking that it would run its course but im not to sure about that anymore as it hasnt decreased in size.
I am assuming it has something to do with the tank being somewhat new, however cant determine the exact cause. I was very careful not to let any phosphates or any silicates in (even when curing the new rock).

Im assuming the biofilm is either bacteria (highly likely) or diatoms that just wont subside (not as likely). what do you all think?

 

It's hard for me to see, but is it a hair algae? I see it swaying in the video, but I can't really see it well, or see what color it is, etc.

 

it has been colorless for all three weeks so i am thinking no to hair algae... i believe hair algae would require a color so it can go through photosynthesis.

 

Yes, it would be some type of green/yellow....

I'm going to guess some type of bacteria. It kind of reminds me of cyano, but not red. So I'm going to go with bacteria.

 

Is it spreading at all?

I thought by it's coloration it might have been a type of sponge or other simple live-rock encrusting fauna, but the way it moves is like an algae.

edit: can you get a really close up pic of it? Could it be a hydroid colony of some sort?

 

Hydroid is my best guess

 

A friend has that too, I'd say it is a type of algae, probably came on the rock. Do your fish nip at it?

 

are you dosing vodka in this tank?

if you are, its probably a bacterial growth from the excess carbon

 

- i am fairly certain it is not algae
- my rock came straight from my old tank (where this Biofilm was not present) and my new rock is base rock that was formed into pillars (see my 2010 diy video entry) and then cured in a plastic tub for a few weeks
- I have not yet dosed vodka, however am tempted to start up and see if I can deprive them of whatever nutrient fuels this stuff

 

I don't think it's a type of hydroid. I have never had them in any of my tanks and I haven't added new "live" rock to my systems in over a year.
It's on almost all of the rocks which also leads me to believe it is not hydroids