Advice with brown/red hard to physically remove algae

[ebrg87]

Hello reef2reef
I've been hovering around for quite sometime and just decided to active participate on this incredible forum since I'm unable to solve this algae problem for the moment.

My sps reef is relatively new (6 months) and I've started with curated live rock from a very good local store ( I'm located near Paris in France). Added some substrate a couple of days before and 4weeks later I added some AF pink dry rock (biggest mistake I think and problem source) very coarse, because I didn't wanted to go BB and wanted to apply a lot of flow.

Fastforward to 2-3 month ago +-, I have added a lot of sps frags and only 3 fishes (gem tang, 6line and banggai). I always liked using a refugium so chaeto is growing very well. Because of the low bio load, refugium and quite some sps frags I've started dosing nitrates and slightly some PO4 along with aminos. It was a quick success since frags stated encrusting and, color-up and I had found a good equilibrium with light feeding + dosing NO3 and PO4.
After 3-4 weeks some corals started to go pale (mainly montipora) so I tested potassium. Indeed it was depleted, so started slowly dosing it too. From that point algae was still under control and I kept this routine.
1 month ago I had another sps frag batch and decided to icp test (results below). Salinity was low (my refractometer is consistently showing 1.026 but who knows...) so I slowly corrected that. A part from this some trace elements were off. I had K+ and A- from tropic marin and decided to dose it too. Very slowing ramping up to recommended dose.
After this small story, we are as of today. This brown algae is taking over but mainly on the AF pink rock. I've looked around and didn't find exactly what kind it is, so any help is
appreciated.

I saw some Silica in the results and RO water but this doesn't look like diatom. This is VERY hard to remove from rock, almost impossible even with a toothbrush. In the microscope nothing is moving so no dyno, no bubbles etc...

From all this anyone has any suggestions? CUC eats a little but for the time being cannot compete. My idea is that the substrate is not adequate and may have accumulated to much detritus and it's feeding the ammonia to this algae...

 

[wculver]

It actually looks like a diatom outbreak. Some colonies are typically pretty hard to scrub off rocks and/or glass. My RO/DI water has silicates in it so I have diatoms pretty regularly on the glass and have to use a scraper for the more aggressive spots. It is odd that you say it is only growing on a certain rock type. Perhaps that rock has a better chemistry for growth?

Question: Do you have this growth on the glass also?

 

[ebrg87]

Hi,
For me diatoms are not hairy like this, but maybe I've not seem all of them. For sure looking at the microscope picture and comparing to the "pennate diatom type" I'm not that far I think.

It's not only growing on a certain type of rock (AF pink rock) but it's "mainly" on those type of rock. The real curated live rock is also seeing some of this algae but not as many as the AF rock. Maybe the fact that it's artificial, who knows.

On the glass I get a film like brown algae but very easy to remove with a mag float. I have to clean maybe one every week, but not out of normal.

Since I'm already running low in PO4 I would like to avoid GFO. Any other suggestions on the silicate clue without removing PO4? BTW I have a lot of sponges on my sump and snails are growing fast, which I think could be a silicate indication too, right?

Any thoughts on GFO as last stage on my RO DI? I'm already reading 0 after my DI resin, but maybe Si are passing anyway.

 

[Miami Reef]

It doesn’t look like diatoms to me, but I’m thinking it looks like chrysophytes. I have a similar appearance but not as progressed as yours.

 

[Miami Reef]

This is chrysophytes, looks like tiny non-motile cells.

 

[ebrg87]

Under the microscope they don't look at all like this tiny non motile cells. For sure I see no movement under the microscope (I looked for 5min lol).
The macro aspect it's close to what you said but the micro I'm not sure...

I removed a small rock and tried to remove this... Even with a hard steal brush it's difficult to scrape it. Never seen this before

 

[Miami Reef]

Under the microscope they don't look at all like this tiny non motile cells. For sure I see no movement under the microscope (I looked for 5min lol).
The macro aspect it's close to what you said but the micro I'm not sure...

I removed a small rock and tried to remove this... Even with a hard steal brush it's difficult to scrape it. Never seen this before

Wow. I got no idea.

@taricha I bet he’d know.