Identifying brown / red patch on rock

[ashtoreth]

Hi,

I've had my tank up for 3.5 months now and just recently noticed a slight patch of brown/red on some of my rocks (started with dry rocks and this was not on the rocks a month ago). It's red under blue light and brown under normal light (see pic below) -- but seems like a very light layer (not hairy and doesn't have tufts I can pick off). Do folks know if this is a specific type of algae / should I be trying to remove it some specific way?

My tank parameters are below and in terms of current inhabitants, I have two clowns, one firefish, one cleaner shrimp, a few zoas, two mushrooms, one dunkin, one blasto merletti and GSP (GSP has not opened up for some reason).

Temp: 77F
Salinity: 33.7 (was running it at closer to 34-34.5)
Phosphate: 0.01ppm
Ph: ~7.8-8.0
Ammonia: 0
Nitrite: 0
Nitrate: 10-20ppm (should be very close to 10 based on the color in the API test kit)
Alk: 7.6 dkh
Calc: 460-470
Mg: 1370

For what it's worth, I do weekly water changes of 10-15% and so far haven't seen any major algae breakouts. I've been cleaning off a tiny bit of dark green algae from another part of the rock from time to time and my return pumps have either a bacterial or clear algae slime that sometimes gets pumped through when they break off but nothing in the display portion.

 

[Idoc]

The brown patch looks like possibly diatoms... no big deal, it will go away on its own. It should blow off the rocks easily with a turkey baster.

Some of the red in the pic could be coralline starting.

 

[ashtoreth]

I did blow off the pieces during a water change and tried to siphon out as much as possible but it looks like smaller red spots are now on other rocks (presumably I was not able to siphon all of it out). Do I need to limit lights or will weekly cleanings keep it in check until they go away?

 

[Kinjirra]

That brown looks just like the Diatoms I had in my tank...few astrea snails polised my rockwork right back up...they are like floor scrubbers.

 

[ashtoreth]

Thanks that's helpful. Guess I'll stick to weekly water changes and wait it out and see when my CUC can arrive. I was waiting for the tank to have stuff for them to munch on before getting them but sounds like now's probably the right time. I noticed these very small bubbles today on a rock with more red patches -- do folks know if this is bubble algae or just small bubbles stuck to the diatom (looks like ~2mm in diameter)?

 

[Kinjirra]

My Diatoms made little bubbles.....they go away if your cut your light. Algae turns CO2 into O2(bubbles) with lights on.

 

[ashtoreth]

Ah, got it. Thanks!

 

[ashtoreth]

The stuff on my rocks have been coming off and the rocks mostly look better vs. a few weeks ago but I've had some spreading on sand and a few bits of hairy looking ones still on the rocks. It was getting better this past week but seems to be making a comeback on the sand. I just rechecked water parameters and seems like phosphate levels are much higher than what they used to be (0.08ppm vs. 0.02 last week) and nitrates are much lower (was closer to 10ppm and now is between 0-5ppm). Is this normal? I removed my filter pads once a week but it seemed to be getting full with the brown stuff every few days so perhaps I need to replace more frequently? Should I be doing more frequent water changes to bring phosphate levels down so other algae don't overgrow my corals?

Current tank parameters below:

Temp 77
Salinity 34.1
Ammonia 0-0.25 (I'm using the API test kit and it's looking a tinge greener than pure yellow 0ppm but my tank has been cycled and up for 4 months now and have 3 fish, 1 shrimp and some coral so not sure if it's possible that something could've driven an ammonia spike? Nothing died as far as I can tell but I did recently add a batch of additional new corals, but not sure if the diatom die-off of the rocks could've caused this?)
Nitrite 0
Nitrate 0-5ppm (closer to 5ppm)
pH 8
Alk 8.3
Calc 480
Mg 1380
Phosphate 0.08