Help With Diatoms

[rock_on]

I've been battling with diatoms on my sand for about a year now and I can't beat them. The tank is 6 years old established mixed reef.

They aren't bad in the morning but become darker towards the end of the lighting cycle.

Things I've tried:

3 days of darkness (helps but they come back in a week or so)
Siphoning sand
Leaving sand alone
Water changes
Fewer water changes
Remove carbon dosing for a couple of weeks
Remove GFO for a couple of weeks
Replace GFO with Phosguard

Parameters

Calcium: 375
Alkalinity: 8.4
Magnesium: 1300
Nitrate: 1.5
Phosphate: .01
Salinity: 1.024
PH: 8.2

If anyone has some ideas I would love to hear them!

Thanks.

 

[Michael Hoaster]

How's your clean up crew? It's good to have a diverse selection of reproducing snails. Sand bed-specific critters like a Fighting Conch or a Sea Cucumber could help. Micro Serpent Stars reproduce and are great detrivores. Bristletooth Tangs and Dwarf Angelfish would also go after diatoms.

How big is your tank? I ask because a cucumber would starve in a smallish tank. And the fish suggestions wouldn't work in a small tank either.

Another possibility is that they aren't diatoms. They don't usually last a year. They look rather golden, rather than rusty brown. I hate say it but they might be dinos. Do they get bubblier and stringier later in the day?

 

[rock_on]

Thank you for the response.

My tank is 90 gals and I have various snails, a fighting conch, hermit crabs, and a serpent starfish. The Hippo Tang and Foxface will pick at it but they're not really interested. I also have watchman goby that stirs up a section but it continuously stays the brownish color.

I haven't not any bubbles or string-like patterns. I was leaning towards the Diatoms with the reaction to the light, but investigating the possibility of Dinos is worth a try.

 

[Michael Hoaster]

No stringy bubbles is good! After looking at your pics again I think it is diatoms. Sorry for the dino alarm!

A dwarf angelfish might help. I'd also consider adding about 1000 pods. They can refuge amongst the large crushed coral gravel and eat.

Chronic diatoms would seem to indicate high silicates. You know what also like silicates? Sponges. You could add sponges to compete for silicates. But sponges are challenging. The ball and ear sponges are the easiest, I believe. Consider adding one, and see how it does.