Coral bleaching and symbiotic algae.

[magdelan]

Problem:

I have noticed that my corals are all looking a bit (ok, a lot) washed out. After researching "coral bleaching", I have come to understand that when corals get TOO much light, they no longer NEED as much zooxanthallae for energy. So, in return, they expell it seeing that they are now getting their energy straight from the sun (or T5's in my case).

My light:

I have a 4ft Tek Light with 6 Giesman bulbs. Two are Aquablue Plus and Four are Actinic Plus.

Concern:

I am to the understanding that the Actinic Blue's have enough PAR where I don't need to worry about it. DO I?

If my bulbs are not delivering enough PAR, then my whole theory about my corals "bleaching" is out the window.

Do I need another Aquablue Plus and maybe a Midday bulb... or a combination thereof?

 

[GMaquarium]

Im not sure I follow about corals getting energy from the sun after expelling zooxanthallae. Too much light, maybe even coupled with low nutrients could do it.

Cutting down on light will help. Run a shorter photoperiod and less lamps. If its lps corals that can eat, feed them.

 

[Gary Majchrzak]

fwiw

fwiw

Colors of corals grown in greenhouses are usually spectacular- and those corals are receiving a lot of intense lighting (sunshine!) over an extended photoperiod in summertime.

I associate high temps and/or low alkalinity with coral bleaching.

I have several corals (Pocillipora, Acropora, Montipora) that are 20" or less from a 400w MH lamp that burns 12+ hours a day and their coloration is intense. Now... if you're talking about placing low light level corals under bright lighting I would expect some problems...

 

[magdelan]

For the record, a clue (other than testing the alk) that your Alk is low is if it precipitates. Correct? If this is true, then I have low Alk as well as intense lighting.

I raised my lights up about 5-6 inches. I just need to test my alk.

 

[Gary Majchrzak]

you cannot tell if alkalinity is high or low simply from precipitation forming.

I don't think lighting is the cause of your corals looking "washed out" unless the corals are new introductions placed up high under your lighting.

 

[RyanEG]

Im a relative numbskull when it comes to corals but do any of the more knowledgeable posters see an correlation between testing at zero nitrates and these colorization/bleaching issues?

 

[Gary Majchrzak]

there's probably a correlation between absolute zero nitrates and phosphates and coral coloration.

With fishes being fed in the aquarium I find it difficult to believe Mike has absolutely zero nitrates or phosphates.

I tend to believe that the recent water changes somehow had something to do with the washed out appearance of his corals... but that's just speculation on my part.

 

[GMaquarium]

Mike mentioned to me not too long ago that he just switched to t5 lights. So six new lamps alone can change color of corals. Coupled with low nutrients like I said before. Especially if the low nutrients are a new thing in this tank. Perhaps feeding the tank more would help with color, yet nutrient reducing methods (large waterchanges, carbon dosing/media ets. and po4 clean up) all still need to apply. Think High nutrition, low nutrient.

 

[magdelan]

I'm taking it all in right now. G is correct. Unless we forgot, I had a 180g that I took down in the fall. All of those corals were held in my 120g sump with a very minimal photoperiod. This was acheived with a 4 bulb Tek Light that I borrowed from TRS while my new one was on order. If I recall, my intention was to let any nuisance algae on the rocks die off from a shorter photoperiod. After setting up the new 120 and transfering my corals, I set up the new 6 bulb tek tight and if I remember correctly, went right in to a full 8-10 hour photoperiod. Now, months later, my corals look blah. My orange cap is almost light purple with an orange ring. My Incredible Hulk acro looks more like the Tin Man. Euphilia are all washed out aswell. I'm going to test my params tomorrow after work. Who knows, it could be a Mg problem. We'll see.

 

[tmz]

I think a nitrogen deficiency is unlikey in a tank with fish.PO4 in reef waters is only .005ppm so I doubt it's deficient either. If it's high it could interfere with calcification and stress corals.

Significant increases in par(photsynthetically available radiation) without acclaimation for corals used to less par can lead to an expulsion of zooxanthelae. While in dimmer light the coral produces more zooxanthelae to ensure adequate photosynthesis for it's survival . When rapidly exposed to higher light the large zooxanthelae population produce more O2 (oxygen radicals) than the host coral can handle and are expelled for self protection by the host leading to a pale pastel or bleached appearance. The darkening of the montipora may indicate higher zoox levels. Corals acclimated to higher par levels by starting low in the tank and moving them up slowly over the course of a week or two will slowly reduce zooxanthelae populations leading to less browning( all zooxanthelae is brown) and the production of colorful protective pigments without a mss expulsion.

Temperature spikes can also cause zooxanthelae to be overly active with similar results.

Spikey alkalinity is also harmful to stony corals and should be monitored regularly.

I don't think magnesium is an issue but it would be helpful to know the level.

_



Alakinity shifts can also stress sps

 

[magdelan]

After testing alk/ca, I found my alk to be at 9.6 kh and my calcium around 550ppm. I dosed only the alk part of the "two part" for the past three days to bring down the ca. My alk is now at 10.5kh and my ca is at 500ppm. I have already seen a positive response from my sps (coloration and growth tips).

I had a good talk with 'G' about the dirrect coralation (no pun intended) between nutrients, nutrition, and light.

I have a pretty clean tank now (cleaner than ever). I am running a good quality carbon, po4 remover, washing my filterbags every 3 days, and performing weekly water changes. Along with this, I have continued a low feeding regiment. I now realize that with a nutrient low system, I need to increase my feedings to boost nutrition.

Time will tell, thanks for the help!

 

[tmz]

Sounds good.