Help with ID and treatment - diatoms?

[xradikalx]

Hello all,

I come to you after battling for months and being beaten down time and time again. I have a 310g display tank, 40g refugium, 50g frag tank, and 60g sump plumbed together. This is about 1.5 years old, and it is primarily an SPS tank with a good mix of LPS added, as well. For a long time, I suffered from green hair algae. Through daily scrubbing with a toothbrush and aggressive nutrient reduction, I conquered the hair algae. However, after running 0 nitrate and phosphate for a while, I had a dinoflagellate outbreak. I have since allowed the nutrients to drift up which cleared this outbreak, but my tank naturally runs with a nitrate of 0.1 and phosphate of 0.03. Then, approximately 3-4 months ago, I slowly developed the current outbreak. Pictures and videos are included, but this nuisance grower is a dark red/brown filamentous species. It thrives in both low and high flow, unlike cyano. It easily brushes off the rocks with a toothbrush with one swipe, unlike hair algaes.

I have diligently scraped, brushed with a toothbrush, and turkey basted almost daily for 3 months. I can easily clear the growth from the rocks, but it starts to return within hours (not days or weeks). I have tried to push the nutrients higher but can't seem to get above a nitrate of 1 and phos of 0.04, despite dosing ammonium bicarbonate and phosphate. The interesting thing is that my SPS don't really seem to mind whatever this is growing all over the place, though I think their color would be better if I could get my nutrients up a bit.

Current parameters:
Ca - 434
Alk - 8.51
Mg - 1369
Nitrate - 0.9
Phos - 0.01 (on apex), 0.03 (hannah)

I am hoping you all can help me diagnosis this new species. I am leaning towards diatoms. The reason I say that is that I recently did a send-out ICP test and most everything was in normal range. A little low on iodine, zinc, and iron which I am repleting. But by far the most glaring issue was that my RO/DI water came back extremely high in silicates, which are making their way into the tank via auto top off and water changes.

I have ordered a silicabuster addon for my RODI, but any other ideas are greatly appreciated!f

Thanks in advance!

 

[Mr. Mojo Rising]

It looks more like dino's to me with some hair algae mixed in. Can you tell us about your filtration system?

 

[xradikalx]

For filtration,

My overflow runs into 5micron filter socks which I change weekly, on average. There is a filter roll as well to filter out large particulate waste.

I run carbon in a reactor which changes about every 3 months.

Skimmer is a reef octopus 3000xt.

Refugium is in a 40g breeder plumbed into the system which has a ball of chaeto rolling around in it. Only have half the lights on in the fuge to help let nutrients come up.

I do weekly 10% water changes

I have an Aquatop 36w uv sterilizer with a new bulb.

I have attempted both chemiclean and a 4 day blackout. Both knocked the outbreak down considerably (blackout worked better than chemiclean), but a few days after it was just back in full force.

I can say that whatever it is, inverts dont want a piece of it. Inhad 6 urchins and they have basically starved, only 2 left. I used to have an army of pods crawling around, but now they are nowhere to be found.