Can I get an ID Please

[TheDon]

I knew I had seen those before somewhere:
https://www.reef2reef.com/threads/amphidinium-dinoflagellate-treatment-methods.365850/post-4526196

More active but also probably Testudodinium instead of Amphidinium (note that the community always calls them Amphidinium even though this isn't necessarily accurate):
https://www.reef2reef.com/threads/amphidinium-dinoflagellate-treatment-methods.365850/post-6438707

I remember seeing high resolution images of this variety though... but I can't remember the name...
I believe it still belonged to the Amphidiniales order so treat it as Amphidinium for now.

I don't think it will be much harder to "defeat" than other dinos, otherwise I would have seen it far more often, but it is a less common variety in reef tanks.

So silicates and bring on a nice diatom bloom? Thing is if I leave tank it just seems to get worse. Might be best to try and hit them hard now, while there’s not a lot on slides?

 

[EnterName]

So silicates and bring on a nice diatom bloom? Thing is if I leave tank it just seems to get worse. Might be best to try and hit them hard now, while there’s not a lot on slides?

I actually think diatoms are the more probable cause of the discoloration so far. They aggregate and become visible to the naked eye which matches your detritus + diatom findings. The few dinoflagellate cells you see are probably less of an issue at the moment. A few cells are totally normal and not harmful, they are part of the natural food chain. If you are still worried you can add silicates, but this will worsen the brown stains on your substrate.

I also found more like yours: https://www.reef2reef.com/threads/dino-id-looks-like-amphidinium.1006973/