Help Please: Does black sand inhibit coralline growth?

[jason the filter freak]

So in my last tank I had zero coralline growth except on the glass below the level of the sand bed. Myself nor anyone on the forums could figure out a good explanation for that.

I moved, set up a whole new tank, and used fresh bags of Hawaiian Black Arag-Alive! Live Reef Sand. 4 months in no coralline algae growth to speak of. I've tried two bottles of Helix (figured it was snake oil anyway), I have no hard corals whatsoever that could be taking up Ca and large quantities of trace elements.



The tank gets a 20% water change with Reef Crystals every 3-4 weeks (I don't bother to test after the tank stabilized) so Ca, Mag, Alk, and trace elements shouldn't be an issue. The tank pH fluctuates between 8.1-8.3 pH night and day. 80 gallon tank with 80 ish lbs of Carbisea life rock* and a few lbs of actual live rock to seed the tank.



Any ideas. Could it be the black sand, or a hex/curse?

[FishingandReefing]

Maybe there are expert can help you out better. My rocks are close to 4 years old and now the coraline just started growing more. Granted that I only started dosing kalk 2 years ago but still. My cal usually sits at around 435-450.

On a side note, I have heard that black sand is magnetic which inhibit the growth of sps and coraline is similar to sps so


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[jason the filter freak]

4 hours ago, FishingandReefing said:

Maybe there are expert can help you out better. My rocks are close to 4 years old and now the coraline just started growing more. Granted that I only started dosing kalk 2 years ago but still. My cal usually sits at around 435-450.

On a side note, I have heard that black sand is magnetic which inhibit the growth of sps and coraline is similar to sps so


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Oh yea magnetic. I've had many a scratch on previous tanks that can attest to that. Its a god awful noise and a sinking feeling in your gut when you hear the "screeeeeeee" noise of moving an algae scraper across the glass that has magnetic particles stuck under it. 

[jason the filter freak]

Tank is also nearly 6 months old now that I look back at my Apex logs. 

Edited May 14, 2020 by jason the filter freak

[lynn.reef.nerd]

I have the same black sand in my 65 gallon. Tank started oct 2019. Full of coralline by around 3-month mark. I keep mainly acros in that tank right now.

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[Delphinus88]

Seed your tank with coraline shavings from another tank that has it growing on the glass?   

[jason the filter freak]

27 minutes ago, Delphinus88 said:

Seed your tank with coraline shavings from another tank that has it growing on the glass?   

Did not. I've asked and or begged for someone in the area to scrape their tank and or sump for biodiversity and or coralline no dice. The reef scene is miniscule around here. Especially compared to WAMAS. I have definitely seeded with smashed up live rock with heavy encrusted coralline growth though.

[lynn.reef.nerd]

I thought of something else also. I have a softy/mushroom tank that is not tied into my main system. No dosing and no acros. That tank has been up for over a year, but no trace of coralline.  I move corals back and forth between the two system, so I am sure there are traces of coralline passed between the tanks. Not sure if that helps with anything.

[makai531]

I’m going to do some corraline scraping off of the glass next week, now that I’ve moved some fish around. I can give it to you if you are close. I’m in Annapolis.


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[jason the filter freak]

@makai531 Very kind of you to offer (seriously). However I currently reside in Oahu, HI. So it'd be a bit of a schlep.