Acropora tip burn

[Flipside]

You know what else it might be? too much circulation blowing in one continues direction at the coral tips. Are you running some type of wavemaker so you dont have your powerheads blowing so hard continuesly off the tip or your corals.
maybe your temperature fluctuates too much? all these things I mentioned could have a great deal on the matter. maybe all or some combined. or your PH as well. You didnt mention your PH. maybe its too low or too high or it fluctuates between lights being on and off.
Worse case, you should take the burnt tips off to prevent spreading. otherwise you'll loose the whole piece. those are nice collection you got ther.

[Doug]

Tony, I wonder if there is an answer. Most of these threads and there seems to be many, seldom have a conclusion, when a seasoned aquarist like yourself is involved. Of course, many newer ones, make some visible mistakes, that we can help with but the ones like you, usually have enough knowledge to cover all the bases.

I read your thread on RC and similar answers over there, as on all the similar threads on sps problems like yours on the RC sps forum.

I wish I had an answer for you from reading most all of them over the years but dont. Just looking at them to me, looks like burn/bleaching from excessive light at the start. Not saying thats the cause but what it looks like. I cant see them receding like that from not enough light, old bulbs, or anything of that nature.

Definitely, as mentioned, abrupt alk. changes to the corals could cause it. As for the uv working, if you remember when the newest bare bottom fad [not the one we did back in the early 90,s. ], began, most of the experienced reefers promoting the system, also said using uv was a large part of it. If you check some of those large threads on RC in regards to it, most had mention of them.

I cant personally say if they help, as its been 20 yrs. since I used one, but the evidence from them and others like Sam, may show some truth in it. Mind you these were high flow bare bottomed sps systems.

As for ozone, does it not remove organics, similar to carbon? Always thought that,s what it was for. So if your problem is bacterial, then the sterilizer would be the way to help. I have thought about getting a small hang on unit for my nano. The one problem with UV units, is not changing bulbs soon enough, and/or premature bulb failures with some models. Plus I thought I read once about salt reducing the light emitted and models with the wipers to be far superior. [ just trying to remember things here].

[Delphinus]

Thanks Doug. I agree that the two most likely explanations for what I'm seeing would be light burn and alkalinity burn. If it was someone else's tank those are what I'd be suggesting to look into.

My biggest worry about this whole thing is that, whatever it is, seems to transfer from one tank into another. I have 3 distinct reef systems at the moment and none of them are capable of sustaining acropora species. I do have montipora's, seriatopora's, and pocillipora's that seem OK. In fact a "test frag" of birdsnest I received from Snappy about a year ago has turned into a reasonably sized colony in my 75g. But any acropora's are toast.

This is why I'm personally leaning towards some kind of pathogen as an answer, it's just that I wish there was a better way to confirm and overcome before my new tank becomes the same acropora-free zone that the others are. If it is pathogenic in nature then moving clams and fish and the surviving corals into there are likely transferring the cooties as well.

So, maybe the UV is still the answer. Unfortunately the cost is beyond my means at the moment so the idea will have to wait for now.

Flipside, here is some additional info for you. You're right I forgot to post pH. Here is that info. I was asked the same question on RC so I went and did some testing (I rarely test pH since I've never seen a reason to - it's usually a parameter that is in response to other parameters - depressed pH might indicate high NO3 for example and/or low alkalinity - so I focus on those parameters instead). But anyhow, this is what I found:
pH at end of day before lights out = 8.4
pH in morning two hours before lights on = 8.1

I found that when I was running a reactor, these numbers would be pulled down somewhat (ie. range would be more like 8.2 to 7.8 or so). Right not I am not running a reactor, I dose Ca and Alk manually. Those are the only additives I use. I dose Ca in the morning (Seachem Reef Advantage) and Alk at night (Seachem Reef Builder), I test Ca and Alk every few days and adjust the dosage amounts accordingly if the numbers drift away from target. For the most part it's a steady state though.

The tank in question is not currently running wavemakers. Although FWIW, it did have Tunzes on a multicontroller in the past and that did not seem to make a difference at the time, also my other tanks do run wavemakers. Nevertheless maybe I will see if I can change things around to create less of a steady state flow situation in this cube tank. I don't disagree that this could be a contributing factor, thanks for the suggestions.

I will check my daytime and nighttime temperatures and see if there's a fluctuation at the moment. I don't think there is a significant fluctuation but it's been a while since I checked daytime versus nighttime. I try to run the tank around 76F.

[PoonTang]

Mabey try dosing smaller amounts multiple times per day. Perhaps you are shocking the system too much with just the 1 large dose. I think that most Alk suppliments have a large affect on local pH.