Does the potassium in 458 ppm can cause these corals to be brownwish?

Does the potassium in 458 ppm can cause these corals to be brownwish?
The other parameters are: (test red sea pro)
PH 8.2-8.4
KH 11.2
Ca 430
Mg 1450
NO3 0
PO4 0.04
K 458
I 0.06
Fe 0.15
I add trace elements daily and feed with oyster feast daily too.
Pink stylophora

Superman Montypora

Yellow Millepora

 

Potassium test kits are about as inaccurate as test kits get, next to say iron and Iodine. The range your in, is fine, normal seawater is about 400ppm, so just a little high, if the test is accurate. From some independent testing, it seems IIRC most potassium test kits are only accurate to about +/-100 ppm though. So, you could be anywhere from 350-550ish LOL. Generally though, browning is a result of nitrate or low light.

 

These corals are under MH XM 250W 15,000K in an aquarium 16 inches deep. The reflector that I use is Hamilton Cayman. The bulb is 3 months.

 

First, to be honest, the corals you point, out don't really look brown to me, at least on my monitor. More just dark, actually probably about their natural color, again, at least on my monitor....

Nitrate tests aren't accurate either BTW, or there could be some local die-off on the rocks, causing a proximity exposure to nitrate, but it's diffusing in the whole tank and is therefore not detectable. Or the corals are lower and shaded etc...

Could be something to do with trace elements. Potassium hasn't scientifically been shown to have any effect whatsoever on corals, neither have most "trace elements". We simply don't know what they do, but anything is possible. Some people do say potassium helps the reds, which when red gets darker, combined with some yellowing of the water, perhaps could look brown... No one can really give you a definitive opinion though, just their opinion, as there is really no data in that regard.

There is data in regards to other compounds and lighting. Nitrogen compounds such as nitrate are definitely associated with browning. Phosphate surprisingly isn't generally. I'm not aware of data with regards to Iron, but it definitely drives algae and could therefore definitely drive zooxanthellae causing browning. So, therefore could be and your iron is quite high So, I would suspect that before K, if not N, or light. Just a guess though.

re: nitrate test kits:
http://www.reefcentral.com/forums/showthread.php?t=2017544

Edit: BTW, I just picked this thread randomly, for Randy's comment on nitrate kits. This probably wasn't a great thread to pick, but if you look around, there are lots of discrepancies in nitrate kits.