Polyp extension (or lack of)

[Acro_Al]

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!

Thanks,
Al

[G.Alexander]

Welcome to ZeoVit.com !

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 ?

G.Alexander