Dinos or Diatoms?

[rbendikas]

Hey, started seeing some spotting on the sand that looked like rust. Now it grew into this, looks kind of like hair. I'm new to the hobby and the tank is maybe 1 month old. I also tested SiO2 and it's quite high (>6). I hope it's Diatoms but could someone else have a look?

 

[Gumbies R Us]

Photos under white lights?

 

[rbendikas]

Apologies, adding additional photos.

 

[Reefara]

I’d blast them with a turkey baster on the sand

Do you run uv stabilizers??

Also it a new tank. Most definitely needs to go through its phase. Just make sure to not over feed the tank and prove the algae with more nutrients.

 

[Gumbies R Us]

Apologies, adding additional photos.

Sandbed just looks like typical new tank ugglies. I wouldn't worry about that. The back wall looks somewhat like GHA.

CUC members?

What are your nitrates, and what are you using to test?

 

[Reefara]

Quick tip

Increase flow to areas that have an abundance

 

[rbendikas]

Sandbed just looks like typical new tank ugglies. I wouldn't worry about that. The back wall looks somewhat like GHA.

CUC members?

What are your nitrates, and what are you using to test?

These are the logs, I'm using Red Sea Marine Care test kit and JBL for SiO2. The bigger one was done at the shop.

27/02/2026 Ammonia 0.1


05/03/2026 Ammonia 0.2


07/03/2026 Ammonia 0.2 NO2 0.0 NO3 0.0


09/03/2026 Ammonia 0.5 NO2 0.0 NO3 0.0 SiO2 >6.0


10/03/2026 Ammonia 0.7 NO2 0.0, NO3 0.0 PO4 0.03 Ca 425 Mg 1260 KH 6.1 PPT 33


11/03/2026 Ammonia 0.8 NO2 0.05


12/03/2026 Ammonia 0.5, NO2 0.05


13/03/2026 Ammonia 0.4, NO2 0.1


15/03/2026 Ammonia 0.2 NO2 0.1 NO3 1.0


16/03/2026 Ammonia 0.1 NO2 0.0 NO3 0.0


20/03/2026 Ammonia 0.1 NO2 0.0 NO3 0.0

 

[Reefara]

Sandbed just looks like typical new tank ugglies. I wouldn't worry about that. The back wall looks somewhat like GHA.

CUC members?

What are your nitrates, and what are you using to test?

Honestly your ammonia should be at 0.0

One thing I might say is prob there isn’t enough beneficial bacteria occurring and you keep repeating the cycle.

Have any fishes or anything?
Anything has died?

Add some Tim’s or microbacter7 to increase the rate of bacteria

 

[Reefara]

Sandbed just looks like typical new tank ugglies. I wouldn't worry about that. The back wall looks somewhat like GHA.

CUC members?

What are your nitrates, and what are you using to test?

These are the logs, I'm using Red Sea Marine Care test kit and JBL for SiO2. The bigger one was done at the shop.

27/02/2026 Ammonia 0.1


05/03/2026 Ammonia 0.2


07/03/2026 Ammonia 0.2 NO2 0.0 NO3 0.0


09/03/2026 Ammonia 0.5 NO2 0.0 NO3 0.0 SiO2 >6.0


10/03/2026 Ammonia 0.7 NO2 0.0, NO3 0.0 PO4 0.03 Ca 425 Mg 1260 KH 6.1 PPT 33


11/03/2026 Ammonia 0.8 NO2 0.05


12/03/2026 Ammonia 0.5, NO2 0.05


13/03/2026 Ammonia 0.4, NO2 0.1


15/03/2026 Ammonia 0.2 NO2 0.1 NO3 1.0


16/03/2026 Ammonia 0.1 NO2 0.0 NO3 0.0


20/03/2026 Ammonia 0.1 NO2 0.0 NO3 0.0

Honestly your ammonia should be at 0.0

One thing I might say is prob there isn’t enough beneficial bacteria occurring and you keep repeating the cycle.

Have any fishes or anything?
Anything has died?

Add some Tim’s or microbacter7 to increase the rate of bacteria

 

[Mr. Mojo Rising]

do you have fish in the tank? I'm wondering how you basically have zero ammonia and zero nitrate. How did you cycle the tank, what kind of bacteria and ammonia did you use?

How did you measure silica? I didn't know that was possible, thats interesting. The high silicates will come from the new sand, its normal, diatoms feeds on silicates, so when they exhaust the silicates the diatoms will die out on there own, usually takes a week or two.

 

[rbendikas]

Honestly your ammonia should be at 0.0

One thing I might say is prob there isn’t enough beneficial bacteria occurring and you keep repeating the cycle.

Have any fishes or anything?
Anything has died?

Add some Tim’s or microbacter7 to increase the rate of bacteria

So my shop told me to start with 2x tiny hermits and 5x trochus and I've been putting a little fish food to keep them happy + introduce some ammonia. I also have GST and ricordea in the tank (also suggested by the shop). The cycle seemed very weird in the sense that Ammonia spiked, but NO2 and NO3 never increased significantly. The shop suggested adding first fish after 6 weeks of starting the tank once the water parameters stabilise. So far everything is alive and seem happy. I keep adding Arka Nite Out II live bacteria (Tim's is not available is Switzerland). I have a filter sock and a skimmer, but no UV at the moment.

 

[Reefara]

Honestly your ammonia should be at 0.0

One thing I might say is prob there isn’t enough beneficial bacteria occurring and you keep repeating the cycle.

Have any fishes or anything?
Anything has died?

Add some Tim’s or microbacter7 to increase the rate of bacteria

So my shop told me to start with 2x tiny hermits and 5x trochus and I've been putting a little fish food to keep them happy + introduce some ammonia. I also have GST and ricordea in the tank (also suggested by the shop). The cycle seemed very weird in the sense that Ammonia spiked, but NO2 and NO3 never increased significantly. The shop suggested adding first fish after 6 weeks of starting the tank once the water parameters stabilise. So far everything is alive and seem happy. I keep adding Arka Nite Out II live bacteria (Tim's is not available is Switzerland). I have a filter sock and a skimmer, but no UV at the moment.

Honestly not bad but what’s the Time frame?

Did you put them in immediately, how long did you let your tank cycle?

6 weeks is already cycled but it all depends on the timeframe.
Most times you put things immediately it does help but with added additional bacteria that allows for that chance.

 

[rbendikas]

do you have fish in the tank? I'm wondering how you basically have zero ammonia and zero nitrate. How did you cycle the tank, what kind of bacteria and ammonia did you use?

How did you measure silica? I didn't know that was possible, thats interesting. The high silicates will come from the new sand, its normal, diatoms feeds on silicates, so when they exhaust the silicates the diatoms will die out on there own, usually takes a week or two.

Regarding the fish, please see my reply above. For silica measurement, I used this test kit: https://www.zoo-roco.ch/jbl-sio2-si...Kd1RB5hvVr-CKgVTbV-RVpxNBMG6D2yAaAg1kEALw_wcB

 

[rbendikas]

Honestly not bad but what’s the Time frame?

Did you put them in immediately, how long did you let your tank cycle?

6 weeks is already cycled but it all depends on the timeframe.
Most times you put things immediately it does help but with added additional bacteria that allows for that chance.

So I added the crabs, trochus and GST, 1 week after starting the tank. That's when the ammonia started increasing. I added ricordea 1 week after the others. It's been maybe around 2 weeks since then. So in total around 4 weeks in. The brown algae showed up maybe ~5 days ago.

 

[Reefara]

Honestly not bad but what’s the Time frame?

Did you put them in immediately, how long did you let your tank cycle?

6 weeks is already cycled but it all depends on the timeframe.
Most times you put things immediately it does help but with added additional bacteria that allows for that chance.

So I added the crabs, trochus and GST, 1 week after starting the tank. That's when the ammonia started increasing. I added ricordea 1 week after the others. It's been maybe around 2 weeks since then. So in total around 4 weeks in. The brown algae showed up maybe ~5 days ago.

Ammonia spikes due to the nitrogen cycle

You are still in a mature stage so you will have swings and def in a take 40g.
Honestly saying let it ride.

Don’t dose
Don’t use white led
8 hr time limit for now
Don’t add bioload for now

Use some added bacteria and let it ride for another 2-4 weeks and see what happens

Test every week

Maybe as a suggestion… if you have enough algae or you can feed it
But a conch
Preferably Tiger conch, they’ll stay small and bulldoze and move the sand around for you

 

[vetteguy53081]

Appears to be diatoms and a normal parts of water chemistry and merely a brown algae that typically appear in a tank which has just completed its cycle but they can also appear in an established reef tank and looks ugly but in most cases are harmless and feed mainly off of silicates as well as dissolved organic compounds, phosphate and nitrates. Tap water can contain silicates and is a good way to get a bloom if you use it to mix salt or to replace water that evaporated from the tank. Using an RODI unit helps, although you can still get diatoms with an RODI unit if the cartridge that removes silicates becomes expired.
Diatoms are typically harmless and can be beaten once their food source is gone.