SPS bleaching

What are is your PO4 at? Ur dKh is on the low end of okay, I would shoot for a solid 8-10dKh.

Sounds like dinoflagellates, they are prevalent at lower alk. Also bosting pH will help combat dino's. and if that is in fact what it is, stop doing water changes, replace small amts of carbon every couple of days and do a few 24-48hr blackouts.

 

I would use Seachem reef buffer http://www.seachem.com/Products/product_pages/ReefBuffer.html

Yeah PO4 is phosphate, and a crucial parameter for sps maintenance. I assume you're using some type of GFO or probiotic/carbon system aren't you?

 

The level of specificity on an API test kit is not precise enough to be diagnostically valuable. The critical range for an sps tank is between 0.04ppm and 0.06ppm. Although, you can get by without ever measuring your PO4 if you have proper filtration in place.
Phos-zorb is alluminum silicate media, if you read the instructions carefully, you'll see that it indicates that it rapidly removes phosphate and become fully saturated after 2 days, after that point, it will begin leaching phosphate back out into the system. With the avaialbility of gfo (grandular ferric oxide) there's no reason to use alluminum silicate media. Gram for gram, and dollar for dollar gfo binds more phosphate and retains it (practially) indefinately.

 

..... sounds spurrious to me lol!
blaxxrunner- have you considered the possibility of AEFW or any other type of disease pathogen? There's really too many variables to consider in this hobby.
I would start by putting small amounts of GFO in with your GAC. Since you will likely replace the GAC every 2-3 weeks (or should be), just use a couple of tablespoons of GFO with it.
Most GFO rxrs can hang on the back of a tank too. GFO is a great place to start with your trouble shooting, and it sounds like it's likely the issue.

 

Thas kewl! GFO is a great place to start with your situation, and phosphate, in my estimation, is likely the culprit.

AEFW= acropora eating flatworms, they're the bain of SPS keepers trade.

learn more here: http://www.youtube.com/watch?v=rrOjKpSZ8PI

lol Sorry I don't have more useful link, but that one is funny!

 

Could lighting be an issue, bulb old etc...?

 

I also suspect that you have nitrates even though your test doesn't register it.  It's common to not have nitrates show up on testing in a system when algae is present as that's what fuels algae growth...  Your lighting may also be getting at the low end.  I suspect you have diatoms as they are commonly found on the sand, rocks and aquarium walls....  Good luck

 

So what's been happening with the bleaching?
What type of phosphate remover are you using and what do the directions indicate for amounts?
Reason I ask is that often phosphate remover will indicate that @ higher dosage sps bleaching may occur.  You stated that the specimens were doing fine and the issue started after you took measures to correct the algae issue.
Your description of the algae also sounds like the bacterial bloom from vodka dosing (which can also burn sps, though typically @ the tips) although you didn't indicate that you were dosing.
Test kits for phosphates are typically a waste of money - if you have algae, then you most likely have phosphates (or a decaying critter) fueling the outbreak.  The kits read zero as the algae is using the phosphate for fuel. I don't believe we have a lab standard kit in the club.
-Eric

 

I wonder if a higher dosage of phos remover only causes bleaching because of the rapid change in PO4 level, I have read that this too can be stressful.
I thought about vodka dosing as a culprit too, although blxrnr never indicated that was the case. But certainly sudden outbreaks of dinoflagellates and cyano are a hallmark of organic carbon dosing.
While I agree that measurable phosphate is often bound in the biomass of algae, I think regular monitoring of PO4 and NO3 are just as important as dKh and pH monitoring. Lamotte phosphate kits are considered laboratory grade.
An interesting thing that can occur with phosphate, is when kalkwasser is batch dosed, that is, poured in in large volumes once or twice a day. It's well known that kalkwasser decreases the solubility of phosphate and causes it fall out as sediment. Unfortunately these phosphates can and often do redissolve (although some new research has shown that increased skimmate alk is associated with po4). This condition is compounded when people batch dose kalkwasser, the po4 becomes concentrated in the sand bed, and before it redissolves it's attacked by algae, often bryopsis and other hair algaes, I'm unfamiliar with the nutritional needs of cyano and dinoflagellates, although I want to say that PO4 contributes.
Certainly a succession of algal communities can thrive because of the concentration of a single nutrient. For example, diatoms aggressively divide with a steady supply of po4 and silicate, when they exhaust their supply, they die and their decay provides NO3 and CO2 for cyano to move in, finally an area devoid of NO3 and other residence may be home to dinoflagellates, or ciliates.
When people have long term success that is suddenly foiled for no clear reason, the solution is usually elementary. There are probably a dozen other scenarios that have to be well adjusted in our maintenance regimes, that we otherwise take for granted.