Red slime Vs. Dinoflaggelates (sp?)

[Delphinus]

It just comes. It may be a response to nutrients but it might not.

It sounds like dinoflagellates. It's horrible to deal with and it's toxic to your snails.

I wouldn't say it's as easy as "lights out" because it can take several attempts and it needs to be as long as you can stand (at least a week). AND your corals will definitely get stressed, AND you'll need to acclimatize your tank back to lighting levels. ie. lights on for 20 minutes, 40 minutes off. After a few days, change it to 30 on 30 off. After a few days 45 on, 15 off and finally (by now it's at least a week post-lights-out-treatment) back to full on.

Lights-out treatment is the only way to deal with dinos. Cyano you can treat with red-slime treatment, dinos will not be adversely impacted by anything like that. You have to starve them of what they desire most, which is light.

Good luck. If it is dinos you will have a very tough slog ahead of you.