Millepora acro progressively retracting polyps

[KGV]

I collect acros and generally have good growth and PE. Except for this millepora coral (see photo). When I got it 3-4 months ago, it started well in the first month, but it has been steadily declining over the last two months. At first, it looked healthy and formed a bit of a base. But then, its polyps started retracting from the base and upwards over several weeks. Now, all polyps are retracted all the time (day and night), and I think that tissue necrosis will start soon.

Interestingly, I saw the same symptoms also in one other millepora half a year ago. All other corals do well. Therefore, these symptoms piqued my curiosity. Does this sound familiar to someone?

My water parameters are nothing unusual and I’d say quite stable.

PO4: 0.06
NO3: 0.6-1
Ca: 430
Mg: 1350
Alk: 7.5 - 8.0
pH: 8.1 - 8.3

I do weekly 15% water changes. I feed the fish such that my PO4 / NO3 generation is balanced by my export. These params even rise a bit so that the water changes reset them to their constant values, which makes me think that there is always availability. I have also a big fish load.

I have an overkill of flow, such that my corals grow very dense and bushy, even my torts. I have Philips coral care lights with PAR ranging from 450 at the top to 250 at the bottom.

 

[Chrisv.]

Hmm. Any idea if the lighting in the spot where the coral is placed is lower par than the tank the coral came from? This is obviously a slow issue...limited number of dials to turn I guess.... lighting, nutrients, flow, water chemistry. Any chance it's under lit?

 

[Waters]

The joy of keeping this species lol. This same thing has happened to every Millepora I have ever tried to keep......looks great for a few months then eventually stops all PE (regardless of how good the other acros are in the tank). Hopefully someone with success in keeping them chimes in......I am starting to think we don't know as much about this species as we think we do.

 

[jfoahs04]

The joy of keeping this species lol. This same thing has happened to every Millepora I have ever tried to keep......looks great for a few months then eventually stops all PE (regardless of how good the other acros are in the tank). Hopefully someone with success in keeping them chimes in......I am starting to think we don't know as much about this species as we think we do.

I've had mixed experiences too. In my experience it's often light related. There seems to be a sweet spot in terms of the lighting (PAR at about 250 in my tanks) where I get good polyp extension, color, and growth. Much below that, I'll get great PE for a while before slowly seeing a decline in PE, then necrosis, then eventually death. Higher than that, I'll get less PE, but strong color and growth.

I've read a lot that long PE is related to gas exchange and that "great" PE during the day is not necessarily a sign of a healthy coral. The logic makes sense to me, but consitently retracted polyps have always preceded coral death in my tanks. The coral in the OP looks bad to me. That's not just limited extension, there's zero extension there. Something seems wrong. But again, I'm as confused by this species as anyone.

 

[Reefer Matt]

I'd try a lower par area. Some acros don't want par above 150 in my experience.

 

[Bucs20fan]

+1 to about 250-300 par is the sweetspot for mine. When it was lower, barely and PE along with 400 plus it closed up.

 

[92Miata]

Has the frag grown at all in your tank? It's awfully leggy looking to me - millis are usually on the dense side. I'd suspect that growth happened in lower light/flow - but if you got it like that, it's not a "you problem".



It's clearly not happy -and the flesh looks thin - and I agree that if nothing changes you're going to walk in some morning and it's going to be bare skeleton. I'd move it - because clearly the current position isn't working - I just don't really have any suggestion as to what to change and in what direction as far as light and flow. If all your other acros are doing great, I wouldn't make tank wide changes.

Don't be super surprised if it RTNs right after you move it though - sometimes its just too late and they give up when you make a change.

I'd also suggest that your tank might benefit from more nitrogen. Acros don't seem to care much about high nitrates, and its absolutely possible to starve them of nitrogen - so its usually safer to run a little higher. <1ppm has some risk. Bumping it up to 5ppm or so isn't going to hurt anything, and may help.


I will say that I've got 2 corals that are probably A.Millepora in my tank - one is about 6" from the top, dead center, underneath 2 XR15s and an XR30 (G3s) over a 24x24 area. It gets absolutely blasted with light and flow. The other one is sitting on the bottom and gets blasted with flow, but not a ton of light. Every time I've tried to move it higher it paled out on me and died. I've literally grown it back from a 1/4" tip like 4 times because there's this stubborn part of me that thinks it needs more light.

 

[Bucs20fan]

I also agree with more nitrates, dont judge, but I try my hardest to keep my nitrates at 10ppm, no issues with my millie or other acros.

 

[92Miata]

I also agree with more nitrates, dont judge, but I try my hardest to keep my nitrates at 10ppm, no issues with my millie or other acros.

Mine were at 42 ppm when I tested them this week. That's clearly not where I want them - I'd rather be 10ish - they're causing some cyano issues right now. But there's a LOT of wiggle room here as far as Acros go.

 

[Bucs20fan]

Mine were at 42 ppm when I tested them this week. That's clearly not where I want them - I'd rather be 10ish - they're causing some cyano issues right now. But there's a LOT of wiggle room here as far as Acros go.

Alot more wiggle room than people let on thats for sure. Funny story, I had a large fuzzy chiton die in my tank, I didnt find it for two days. My nitrates spiked to over 100ppm. Super bad, I know. Only corals that were visibly upset were my torches. Acro and millie looked fine. Now I immediately took action to lower it obviously, but they still had PE even in nitrates that high. Although im sure prolonged exposure to nitrate that high would kill them.

 

[ScottB]

I keep a ton of tenuis just fine. Millis in my tank are either uber robust or dead. I keep acro nutrient/ICP numbers so have not figured it out yet.

From prior experience though I can say if you have AEFW they LOVE my millis at least.

 

[Mr. Roboto]

Millis can also be really targeted by curious fish. I had an angel that ignored mine at first and then once he got a taste for it, he kept them closed all the time, they would come out at night but be retracted all day.

 

[Big E]

A frag like the one pictured would need to be put in the shade as it's already bleached and thin. There is not enough zoo in the skin to protect it. Make sure it's not getting direct light........you want it to turn brown. Once it does that, you can move it out under direct light at the bottom of the tank.

The coral has no ability to get nourishment from it's zoo or polyps which also means it's not getting any oxygen ,amino acid, glucose, ect. for itself, so the only chance it has of survival is per absorption.

The next step is to dose amino acids and bacteria. The bacteria can be eaten by the symbiotic bacteria that resides on the coral. As an example, If you dose MB7 this bacteria consumes nutrients and therefore in a sense becomes gut loaded and becomes a super food for the acro's bacteria to assimilate.

You have to be patient but I've brought back plenty of acros doing this.

 

[KGV]

A frag like the one pictured would need to be put in the shade as it's already bleached and thin. There is not enough zoo in the skin to protect it. Make sure it's not getting direct light........you want it to turn brown. Once it does that, you can move it out under direct light at the bottom of the tank.

The coral has no ability to get nourishment from it's zoo or polyps which also means it's not getting any oxygen ,amino acid, glucose, ect. for itself, so the only chance it has of survival is per absorption.

The next step is to dose amino acids and bacteria. The bacteria can be eaten by the symbiotic bacteria that resides on the coral. As an example, If you dose MB7 this bacteria consumes nutrients and therefore in a sense becomes gut loaded and becomes a super food for the acro's bacteria to assimilate.

You have to be patient but I've brought back plenty of acros doing this.

Thanks for the advice! Following a similar logic, I had frags recover by laying them in the dirty sand bed. Let me try that.

 

[unchin]

There's a chance you have white bugs. It would cause symptoms you're seeing like no polyp extension. Hard to tell from the picture, but I would get a magnifying glass and try to see if those specks that I highlighted are anything.

 

[KGV]

There's a chance you have white bugs. It would cause symptoms you're seeing like no polyp extension. Hard to tell from the picture, but I would get a magnifying glass and try to see if those specks that I highlighted are anything.

I had indeed bugs, but interceptor took care of that and I didn’t see them on this particular frag. Thanks for the input.