What is all this stuff????

This is my 28gal Nano. LR, naked clown, Royal gramma, and a Mantis hidden inside the rock. (on purpose!-lol). It has been running for 1.5 years now and corals used to flourish in this thing, even with PC lighting!
Now I have all this green/brown stuff! I have done many water changes and siphoned out the stuff itself, and it keeps coming back! Sunday I did a complete water change including sifting all the sand and by monday night, it looks like this.
It only seems to grow where there is light. I feed once every other day, very minimal! and target feed the mantis every 3 or 4 days with mysis and a turkey baster.

Temp:81
Salinity:1.024
ALK:9
Phos:0
Nitrate:0

There is new carbon in the filter along with more LR and a large sponge that was also cleaned Sunday. Anyone know what it is? And what do I do about it? Its not cyno. I fought that battle last summer, but have been cyno clean for 4 months.
Help!

 

I'm going to guess it is dinoflagellates - but beyond that, I'm of no help!

 

If you have recently added anything plastic you could have some silicates floating around feeding diatoms.

 

Dinoflagellates (commonly called Snot Algae).

Siphon it out, kill the lights for numerous days, elevate the pH to 8.4~8.5 with Kalkwasser. That will kill it.

 

Killing the light helped with my dino problem. Also check your water source.

 

Thanks! That makes sense since it only covers where the light is shining. I'll do that and update! Thanks!

I have a RODI from BRS and the digital meter is 0 coming out and only half of the color changing resin is brown.
However, I believe I was doing a big no-no. I was making a tub of saltwater for a WC with a heater and a circulator pump as always, and not changing the water for a week or so. Then do a WC with that saltwater. I had usually made salt water one day, and changed it the next. I got lazy and now i am paying for it.
Thanks for your help K+

 

dino crap yuk i have delt with it as others have sead kill the lights for a wile with lights off your ph will drop like others have sead watch it i even covered my tank with a blanket just made shure the skimmer was uncovered i also ran my skimmer wet and most of the junk made it in there cool part is i dont see any coral so your in luck there if you have power heads aim them at your overflow to aid in them makeing it to your skimmer once thay let loose thell float .. who wants to play with reef boogers let the skimmer take it away i almost vomited i had a horible outbreak not to mention i have a bit of a booger phobia

silicates and iron as i have read play a huge part in its groth if you use ro water check your cartrages if you dont its time to get one dont trust your lfs to have great water as i found out there suposed ro water was worse than my tap water i think thay sucked the crap out of the sewer after a rainstorm there ro was 240 tds mine was 130