I can’t see the video, but do you have dinos? Some species release toxins that can kill inverts and fish. The algae could also be potentially responsible for decreased oxygen levels.I just recently lost my purple fire fish randomly one morning and have been keeping a super close eye on the other tank habitants to see if anything else weird happens. Well turns out one of my clownfish looks like he’s struggling. Laying on the sand bed with extreme labored breathing. And then all of sudden they snap out of it like they were in a trance. However they still swim around normal and have been eating normally. I noticed my other female clownfish has done it once before aswell. Yellow watchman goby seems to be unaffected. I’m also having some invert dye off recently aswell. I’m not sure if they correlate but figured it could be valuable info. Also please excuse the ugly algae I’m experiencing right now. Still a semi- new tank.
Salinity - 1.026 (calibrated with Randy’s)
Ammonia- 0
Nitrite- 0
Nitrate- 5.2
Phosphate- 0.03
Ph- 7.8
The invert deaths and fish issues are unrelated. For example, copper leaching into the water could kill your inverts and coral. Have you tested your RO water for anything, or did you do a water change recently with water that could have been contaminated?
If it’s a parasite attacking the gills, I would suspect velvet or brook given the rapid decline of the fish. The problem is both diseases require different treatments. Copper at 2.25 ppm in a hospital tank (do not put copper in your DT with inverts) should knock out velvet, but you will need formalin baths or ruby reef rally for brook.
