Unbeatable algae ID?

sassmastawillis · Feb 7, 2026

Can someone help me ID this algae? Tank is mature, almost 2 years at this point, but I've been battling this algae for the past 6 months without much success. Been running just my skimmer and no filter in my sump to raise nutrient levels. Dosing daily with microbacter clean. Tank parameters (please let me know if anything else is needed):

40 gallon display, 20 gallon sump
dkh: 8.7
Phosphate: 0.09
Nitrate: 20ppm

MikeReefs · Feb 7, 2026

Dino. One of if not the hardest Algea to beat. In fact it’s not an Algea at all. First things first you need to outcompete them. For whatever reason they took hold. If your nutrients P or N bottomed out that could have led to them taking over. Regardless you have to build up your biodiversity. This can be done with bacteria like you’ve been doing. Bring up you P or N if it’s bottomed out. Add biodiversity by adding live rock/sand or AF lifesource mud. Last resort would be to add silicates to create a diatom bloom that outcompete the Dino’s. There are certain stains of Dino that can easily be beat just by adding a UV. Regardless of the strain having a uv would probably help. Best of luck I had Dino’s and it took me months to beat. Dino’s can be toxic so adding some carbon would benefit your system

slingfox · Feb 7, 2026

That is not algae. It is dinoflagellates. Not uncommon to have dinos appear during the first two years of a tank so a month 18 outbreak is not surprising. There are many threads on this board on how to deal with dinos. Test your parameters and dose as needed, run UV, dose silicates and bacteria etc. Most important is manual removal by blasting them off the rocks and siphoning your water through a 5 micron sock and siphoning and rinsing your sand. You will need to do this many times over the course of several weeks or a month or more. One thing not commonly mentioned but has worked really well for me is hanging sheets of aquarium fleece on the glass. This provides a surface for the dinos to stick to. I then rinse the floss out periodically.

I dealt with some massive Dino outbreaks during my year and when I used dry rock. When I reset with live rock I had very minor bouts but nothing nearly as crazy. You can fix this issue. It just takes time and manual labor!