Spawning???

I have been having trouble with high nitrates lately so I did a large water change of 20% and then another 40% the following day (yesterday).

Since I have done the water change, last night there was some major things releasing major clouds of white stuff. I have no idea what the things are but they appear from many places, such as beneath the sand, out from between zoa polyps, between rocks etc. These things only expose an orange tube that is between 6-8mm in diameter, and spew out large clouds of white stuff, within minutes the whole tank is cloudy. One of these little orange tube even spat out a glob of orange stuff. This went on for about half an hour. Then tonight at around the same time, the same thing happened?

What is this likely to be?? Any thoughts?

 

Look at youtube videos of Stomatella spawning and see if that looks like what you're seeing.

If it happens tonight get some images please, especially of the "orange tube".

I have also had micro brittle stars spawn after a water change.

Definitely sounds like a spawn though.