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Polyp extension (or lack of)

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  • Polyp extension (or lack of)

    Hello everyone,

    This is my first post and I was hoping someone could recommend some zeovit products to help boost polyp extension and overall coral health.

    I have a 730lt acropora dominant tank which was running well for the last 18 months but lately I have no polyp extension at all, although I am still getting growth. I am DIY balling with Fauna Marin trace elements and 10% weekly water change. I run a caulerpa refugium on 24/7 light cycle and I dose iodine and strontium.

    I suspect my acropora are starving so I have added fish, increased feeding and switched off my skimmer for now. My parameters are solid, tested weekly and my levels are:

    Kh 7.9
    Calcium 460
    Magnesium 1380
    Potassium 370
    Strontium 5
    Iodine 0.06
    Bromine 65
    NO3 & PO4 undetectable by home test and ICP
    No contaminants detected in ICP.

    I have always had low NO3 so I tried dosing KNO3 but suffered from red slime algae as a result so stopped.

    Any advice would be appreciated!


  • #2
    Welcome to !

    Poly expansion can be limited by several reasons so just adding a additive might not fix your issue. I would first rule out that a fish is does nip on the corals as you mention you just have added on fish. Water parameters are basically fine, K+ could be a little bit higher ~ 380 mg but this is not the reason.

    Which corals are affected from this problem, maybe some pictures are helpful also.

    Aggressive carbon or other absorbers can also be he reason also a wrong lighting spectrum, also some kind of material “plastics for example” can leach substances which does lower polyp expansion. Some corals do expand their polys more if iodine is dosed regular. Please also keep in mind that a nutrient poor system like yours do need much less trace elements than a system with elevated levels, maybe you just overdose ?



    • #3
      Thanks for your welcome and response G.Alexander!

      I have ruled out the potential causes you suggested, with the exception of possibly overdosing trace elements due to low nutrients, and this a good point.

      The issue is affecting all my acropora, including some millepora that were previously very shaggy. Nothing in the system has changed, that I am aware of.

      I have restarted dosing NO3 to 5ppm and I can already see some slight improvement, however, the cyano has also started to reappear. I have ordered Coral Vitalizer, Amino Acid Concentrate and Sponge Power to add some additional nutrients to the system. I have also ordered some ZEObak, Cyano clean and Coral Snow to try and deal with the cyano.

      There could very well be something else at play, that I am not aware of, but lets see if the ZEO products make a difference.



      • #4
        I would do a couple of additional water changes lets say 3 x 10% within the next 10 days to refresh elements in a balanced way. You can additional try to dose a Iodine supplement daily for a couple of days.

        Which kind of carbon do you use and how much have you running in your system, do you have the carbon in a reactor ?

        Please also check the K+ level if possible with a different accurate test kit, the level should be ~ 380 mg.



        • #5
          I previously tried additional water changes over the course of several weeks and I didn't see any response. I'll try this again over the next 10 days.

          I dose 2 drops of Lugol's per day as part of my routine which keeps my iodine at approx 0.06ppm.

          The carbon I use is unbranded but in my opinion it is quite strong so I only run a small amount (15 tablespoons) in a reactor for one week each month.

          My K+ is at 370mg on ICP. Do you think raising this would make a difference?

          I started dosing Coral Vitalizer, Amino Acid Concentrate and Sponge Power this week so hopefully the corals will like the additional nutrient load.


          • #6
            If your K+ test result is correct the level of 370 mg should not be the reason of the problem. To rule out the carbon I would recommend to remove it temporary while doing the additional water changes, this will not cause issues. Because of iodine you can try to dose 14 drops every other day for three times.

            Do those corals growing well ?



            • #7
              All corals are growing quickly and their skin looks thick and healthy.


              • #8
                The coral growth is basically positive so my last idea at the moment is a fish which is nipping on the corals, also the trace elements you dose might be a possibility for the issue. Can you stop doing the additional trace elements for some time ?

                Has the temporary remove of the carbon and the higher dosage of iodine shown any improvement ?