Unknown Algae Bloom

[LOZReefer]

About a month or so ago I had a small patch of this red colored algae pop up in my tank. Every time I try and vacuum it out it spreads slightly more and comes right back the next day. Color intensifies as the lights turn on and starts to disappear as lights turn off. It's a rusty red color - not sure if the camera picks up the color very well. See attached images.

My conchs and hermits don't seem to want anything to do with it. I've even placed them directly on the problem area and they do absolutely nothing with it. So far it only covers about 10% of the sand bed - nothing on the rock.

150 gallon tank is 10 months old and so far I've completely skipped any sort of ugly stage. I've done water tests and nothing is out of the ordinary. In fact I would consider them "ideal." 7 fish (1 yellow tang, 1 blue tang, 1 melanurus wrasse, 2 banggai cardinal fish, 2 clownfish), mixed CUC (hermits, conch, nassarius, cleaner shrimp, trochus).

I do make my own water so I'm wondering if this is diatoms and there are silicates in my RODI water. TDS is 2ppm in the output. My next step was to replace membrane and DI filter and do a few water changes to see if I have any improvement. Thought I would post here anyways though.

Any ideas what this is and what I can do to combat it? It isn't becoming an issue but is certainly unsightly.

 

[Mr. Mojo Rising]

I notice it seems to be on one side under the powerhead, but seems more clear on the other side that gets flow. Do you have a powerhead on the other side? It looks like destritus/algae buildup in low flow spots

 

[EnterName]

Dinoflagellates

They are pretty common in young tanks and nothing to worry about in most cases, even though they can become a true nightmare. As long as they just slightly stain the substrate they aren't an issue and rather an indicator that something might be off.

You can start with measuring NO3 and PO4. I assume your nutrients are quite limited right now. This can be both a symptom and a cause of dinoflagellates, so you can try with DIY ammonia (or nitrate) and DIY phosphate stock solutions if your nutrients are actually low. A UV sterilizer might help (depending on species which you would need to identify using a microscope), and if they aren't going away on their own silicate dosing and increasing ORP/Redox can help.

 

[LOZReefer]

Dinoflagellates

They are pretty common in young tanks and nothing to worry about in most cases, even though they can become a true nightmare. As long as they just slightly stain the substrate they aren't an issue and rather an indicator that something might be off.

You can start with measuring NO3 and PO4. I assume your nutrients are quite limited right now. This can be both a symptom and a cause of dinoflagellates, so you can try with DIY ammonia (or nitrate) and DIY phosphate stock solutions if your nutrients are actually low. A UV sterilizer might help (depending on species which you would need to identify using a microscope), and if they aren't going away on their own silicate dosing and increasing ORP/Redox can help.

Area definitely has flow, shouldn't be any detritus buildup imo.

Nitrates are 5 - 10ppm
Phos is .05 - .07ppm
Nutrients have been this way and stable for at least 8 months. I feed very precise amounts.

 

[EnterName]

Area definitely has flow, shouldn't be any detritus buildup imo.

Nitrates are 5 - 10ppm
Phos is .05 - .07ppm
Nutrients have been this way and stable for at least 8 months. I feed very precise amounts.

Nutrients levels seem fine for now, but keep an eye on them.

Diatoms usually don't vanish when the lights go dim, so I'm reasonably sure the stuff contains dinoflagellates. One thing I observe regularly under the microscope is that diatoms and dinoflagellates appear and disappear together. This makes sense because some dinoflagellates can prey on diatoms and may profit from their presence. I assume once you get your TDS down to 0 and manage to get silicate levels down under control in your tank the brown stains will disappear. Slightly stained sand is no reason to worry for now :)

Note: I wouldn't use silicate adsorbers for now as they would adsorb phosphate as well and drain some trace elements.

 

[coralSLover]

Diatoms are usually more brown and dusty and tend to get grazed down, while cyano often shows up on sand beds in tanks around this age even when test results look “perfect.” Slightly increasing flow across the sand, keeping nutrients stable and detectable rather than ultra-low, running fresh carbon, and gently removing what you can without overdoing it usually helps over time. A TDS of 2 isn’t ideal but is unlikely to be the main driver here, and this phase is more common and temporary than it is dangerous.