Stirring sand, Coral bleaching

[bourbeaue]

I have a 165g display mixed reef with 1.5-2in of sand bed. Tank has been fine for 3-4 years. Yesterday for the first time in about 2 years I vacuumed my substrate before doing a water change. I never usually touch it. The water coming out was a very dark grey. Now this morning, a large SPS colony I have (18in diam) has some bleaching (top inch). I was reading on other posts that people were asking reefers with bleached corals if they had stirred their substrate. Not sure how that could cause bleaching. Can someone explain and suggest course of action for my SPS colony ? Should I reduce photoperiod to help it recover ? Should I add iondine ? Anything else ?

I will post photo.

Thanks !!

 

[bourbeaue]

Here is what it looks like:

 

[MrKite24]

Check your water parameters, especially nitrites and nitrates. Stirring your sandbed can cause anaerobic bacteria to die when it is exposed to oxygen which could cause a spike in your nitrate levels. Most people say to leave your sand alone once it is established in your tank. If you need to clean it get some sand sifters (ie starfish or nassarius snails). If you don't like the way the surface looks, just siphon the very surface of the sand to remove and debris. I even get worried when I have to move my sand back to fill in a hole my clown fish have created or when my pumps make a bare spot on the bottom of the tank.

 

[Froggy]

What grain sand are you using?

A 1" - 2" sand bed should be maintained from the start IMO. This includes stirring and vaccuuming. If you have not disturbed it in a long time there was probably quite a buildup in the shallow bed that could not be processed by the bed itself. Shallow beds are limited in this way requiring us to maintain it.

Deeper sand beds are a different story. 4" - 6" beds should not be disturbed in the deeper layers to work properly. You should only clean the top 1/2" in a deep bed.

In your case, it is fine to vaccuum the bed and you should. You probably stirred up some nasties though since you have never done this before and caused a spike, resulting in the coral problems.

 

[bourbeaue]

So what do I do about the bleaching ? Reduce the light for a while ? Will is just return to normal on its own or do I have to do anything special ?

 

[bourbeaue]

So?

 

[seapug]

That's a tough call. Big nutrient releases can cause algae blooms but I've never experienced bleaching from it. The water change you did after would be a more likely suspect in bleaching-- perhaps high pH or alk burns from not mixing long enough? Bad batch of salt? Just guesses....

The best thing to do right now would be to test all your parameters and see if anything is amiss. Personally, I'd keep the same photoperiod you had before the bleaching. The best way to deal with a problem it is to return to the conditions you had when it was healthy.

I also wouldn't let this keep you from continuing to stir the top inch or so of your sandbed as a regular maintenance procedure. IME, it makes the tank healthier in the long run, even if it's messy the first few times.

 

[bourbeaue]

The strtange thing is that only the very top of this particular colony is bleached. All my other SPS are fine. Even that colonoy is 80% fine. I checked my params and they are fine. No Ammonia or NO2 either. Because that top inch is right under my T5's, I figured something in the chemistry made the coral bleach, most likely light induced otherwise it would not have only bleached at the very top of the colony, area closest to the lights...

That's why I am thinking of going easy on lighting for a couple of days, but maybe that's not a good idea. I am hesitating to subjcet the bleached part of the coral to my regular lighting regimen...

Thoughts ?

 

[Cultivatedcoral]

What about your phosphates? You could have released a large pocket and this particular coral was sensitive to it.

 

[aurora]

The DSB is an easy culprit but I suspect your issue is not from the dsb. Top burns in SPS are usually due to change in lighting intensity. Change in lighting intensity at the tip of your coral result from more light reaching it than usual. If you haven't changed your water in a while, the added clarity with a big water change would do it. I've also seen top burns with activated charcoal use. If you haven't used charcoal in while and use a good dose of it, the added water clarity could result in your coral tips getting as much as 25% more light. They essentially get sunburned. Based on your description, I'm not convinced that disturbing the sandbed did it. I have a tankful of SPS and the polyps extends even more for a couple of days following any sandbed disturbance.

 

[bourbeaue]

Aurora,

Your insight sounds good, but haven't changed my carbon it in about 6 weeks. Lighting is programmed by my Aquacontroller and exactly the same every day. No change there either.

Any other thoughts ?

Thanks.

E

 

[dublo8]

How old are your bulbs? Just a thought but many types of bulbs fluctaute their spectrums when new and getting old, this may also be a cause? Im not an expert on that particular subject so i would wait for somebody else to chime in.


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