Your polyps have been doing great for weeks, months, years even, then all of a sudden it happens. Or, maybe you're in your LFS, and you see something you like, but it's bleached or in a pre bleached state. What do you do? Do you throw them out? Do you consider making the purchased of the bleaching polyps at a reduced prices?
What is bleaching?
Bleaching - the mass exodus of large amounts of Zooxanthellae ( single cell algae within our corals which gives them their coloration/pigment ). Almost all of the factors within our reef tanks which result in bleaching are attributed to something we do/did, ....didn't do or should or shouldn't have done. This is but one of the reasons I'm so adamant about education. Knowing the names and prices of every polyp and not knowing the factors which could cause a complete expulsion of Zooxanthellae, to me, is like putting the cart before the horse. Attack me if I'm wrong, but I just replied to an email I got from a reefer who has spent $ 2,000 total on zoas, palys and a few other softies. His goal was to create this monster zoa tank. He purchased his/this first system in June of last year. He's running 250 watt DE - 10 K Halides on a magnetic ballast with 2 - T5 - 6 foot 10 K's as he wants optimal/quickest growth and 2 T5 actinics. He was going to remove the T5 10 K's after a year. He placed everything mid tank level to the top. Unfortunately, he received some very bad advice as most everything has begun to shift/change/bleach/morph, whatever we choose to call it.
Here's a direct quote from page 380, top left corner of Eric's Aquarium Corals book.
"Without the proper number of Zooxanthellae in their tissues, corals must rely almost entirely on dissolved nutrient uptake and heterotrophic feeding to meet their energy needs. Without their symbionts, the corals' ready carbon source produced by zooxanthellae photosynthesis is severely, if not totally, reduced. Furthermore, there is no guarantee that a bleached coral can or will adopt new zooxanthellae. Without the uptake of new symbionts, it will then LIKELY PERISH. At the least, metabolic activity becomes abnormal while the coral is in a bleached or partially bleached state, leading to changes in reproduction, reduced growth and possible tissue degeneration.
Translation - If the appropriate measures by each of us are not taken to adequately address that which leads to bleaching and those who make a concerted effort to cause/create a color shift/change, this is what will potentially happen. The coral will expel its Zooxanthellae from its tissue, the coral will have to rely on organic substrates to get its carbon for growth and development, the coral must now adapt to meet its needs for survival, you have impeded the inner natural functions for survival, there is no guarantee that the color will return and possible mortality ( death ) can occur. The very least that's going to happen is the breakdown of food and its transformation into energy will become abnormal and change and/or alter the reproductive rate, hinder growth and possible cause external damage to the coral.
So what are the contributing factors which causes bleaching?
Factors according to EB which will result in bleaching.
Below is a list of factors which can cause bleaching per EB.
doldrum ( lack of water movement )
red spectral light
Hope this helps someone with a bleaching issue.
Part 2 coming, "Can you reverse the bleached, bleaching process?" Yes, yes you can, it will take time. I have done it and others have as well, providing the coral is still viable, by that I mean alive. Stay tuned for Part 2