Duncan not really extending despite growing another head

[nph]

I have a bio cube 28 with refugium with Chaeto, phosguard and chemipure in the back.

I have Star Poliyps, Ricordia, 2 Blastos, Candy Canes, Torch, Akans and a few rock flower anemones. All look really great except the Duncan.

It is kind of mid aquarium and has medium to low flow.

 

Alkalinity is a little low, no matter how I try I never get it higher than 7-8. PH around 8.1

Really low phosphate and almost NI/NA.

 

Temp is 77. Light is on 7 hours and at a decent low intensity to keep algae in check.

 

What am I missing to make my Duncan a bit more happy?

 

Thanks

 

[seabass]

7 hours ago, nph said:

Alkalinity is a little low, no matter how I try I never get it higher than 7-8...  Really low phosphate and almost NI/NA.

Why are you using Phosguard when phosphate is really low?  And by really low, what is the actual value, and which test kit are you using to determine that?  Also, what is the actual level of nitrate, and which test kit are you using?

 

Similarly, we need to know a lot more about alkalinity.  What salt mix do you use (what was the initial level)?  What are you using to try to raise alkalinity?  What is your tank's magnesium level?  And also, what is the level of calcium?

 

My initial thought, reading the title, with a struggling LPS coral was alkalinity.  Which was reaffirmed by your post.  However, the post also points out a lack of nutrients, with multiple nutrient reducing methods being used.

[nph]

So I just checked my water at my local LFS. 

Phosphate less than 0.1

Nitrite 0

Ammonia 0

Nitrate 0.1

Alkalinity 9

PH 8.1

Calcium 380 (need to dose a bit here)

 

I had a phosguard in there since I recently had some hair algae and from what I can tell it is gone now.

unfortunately so is the cheat... 

 

My LFS suggested I move the Duncan down from the brightest spot where it is now and that might help. What do you think?

Currently it is in the highest location close to the center.

i see the tentacles but quite short.

Or could there be another reason it doesn't really open up with extended tentacles?

[seabass]

Less than 0.1 ppm phosphate could mean anything between 0.09 and 0.00; so I'm still not sure what exactly less than 0.1 ppm means.  Some people want phosphate to be 0.10 ppm, while others might feel that's high and would be more comfortable with a target of 0.03 ppm.  However, less than that could potentially cause problems for other photosynthetic organisms (I.e. corals).

 

Some people would consider 0.1 ppm nitrate low.  But depending on what your phosphate level is, it might be acceptable.  However, with phosphate below 0.03 ppm, that could be a problem.  Low nutrient levels can pose a problem for corals, especially if they are not being fed.  Not all corals should be fed, but LPS corals usually benefit from a small meaty meal (like a mysis) once or twice a week.

 

I'm still very unsure about alkalinity.  While an alkalinity of 9 dKH is fine (many would say spot on), you previously mentioned having trouble getting it above 7 or 8 dKH.  So I'm still not sure what you were using to try to raise it, or what level your salt mixes to.

 

The low calcium number now also has me wondering about magnesium.  As low magnesium will cause additions of alkalinity to force calcium out of suspension (and vice versa).

 

5 hours ago, nph said:

My LFS suggested I move the Duncan down from the brightest spot where it is now and that might help. What do you think?  Currently it is in the highest location close to the center.  i see the tentacles but quite short.  Or could there be another reason it doesn't really open up with extended tentacles?

We might benefit from a picture, to really see what it looks like.  I'm sceptical about the suggestion that too much light is the problem.  I'm even starting to wonder if there is a problem.

[nph]

I moved it yesterday and I already see a small improvement compared to before.

Will start photo this weekend. 

[Saultman]

I have 2 Duncan’s under med to high flow , med light that are doing great 6 new heads each in the 2 months . I also fed them quite a bit mysis and lps pellets 

[SaltyGallon]

Not withstanding the uncertainty regarding your alk (you say it's low, but then up at 9?) I'd say just feed it more. Duncans love reef roids and pellets once they're settled and well fed they really take off. With the only Duncan I ever kept, the individual heads got much larger before it thought about throwing out babies.

[Murphs_Reef]

My duncan seems to stay closed if the flow is even moderate. It likes nutrients p around 0.03 - 0.06 and N around 10

[mcarroll]

On 1/23/2021 at 7:36 PM, nph said:

All look really great except the Duncan.

One of the easiest to grow stony corals there is, so you are correct to sit up and take notice.

 

On 1/23/2021 at 7:36 PM, nph said:

Alkalinity is a little low, no matter how I try I never get it higher than 7-8. PH around 8.1

None of those numbers sound especially low – what is your target for each of those?

 

On 1/23/2021 at 7:36 PM, nph said:

Really low phosphate and almost NI/NA.

This is the problem....be SURE to remove ALL excess filtration from the system at this point.  No more phosphate removers, no extra water changes, et al.  What else are you doing for "tank cleaning"?

 

For the record, neither "low" nor "zero" are good targets....they are dangerous targets.   Nutrients should have minimum levels just like alkalinity does.  0.03 ppm is a decent minimum for phosphates.  5-10 ppm is decent for nitrates.  The only thing I'd add to that is that nitrates are far less crucial than phosphates are, and there doesn't seem to be such a thing as "too high" as long as neither is zero.  Wait, one more thing...."high nutrients" do not cause algae.

 

On 1/23/2021 at 7:36 PM, nph said:

Light is on 7 hours and at a decent low intensity to keep algae in check.

Remember in the future that anything you do to take action against algae like that ALSO works against your corals.

 

Corals and algae have THE SAME requirements.

 

So what keeps algae in check?   Herbivores.  And in a tank scenario YOU are the BMOC of the herbivores....what snails don't clean up (anything already mature) is YOUR job.

 

So give your corals 12 hours of proper lighting and handle the algae yourself (or add a few snails) if it grows.

 

Your Duncan should start looking great as soon as you turn around the nutrient and lighting situations.