Kinda Looks like Dinoflagellates to me (going by the bubbles). More often than not an excess of nitrates and/or phosphates is the problem. A few things I have done in the past to control outbreaks

  • Carbon as a scrubber can help, run actively or passively. I recommend almost everyone use carbon in there sump; run passively at least and changed at regular intervals. It improves water clarity as well as quality.
  • Raised pH can eliminate the problem but perhaps only short term without other issues being addressed.
  • A refugium, if space allows, can go a long way in counteracting dino's as well as many other BAB's that are commonly discussed.
  • Nitrate sponges or some other NO3 remover can be affective.
  • Granular Ferric Oxide (GFO) can be used (with caution) to remove phosphates