Newbie yellow polyp help!

First, I would like to say how much this forum has been a great help in my success in building my first reef. I have been reading posts and threads in this forum for about 2 months. I just want to say thanks to everyone.

With that said, I hope someone could help me with a minor problem. I bought a healthy looking yellow polyp rock that was full with open polyps about 3 weeks ago. I placed it in my tank, and everything seemed fine. All the polyps were opening. About a week after, I noticed some of the polyps were not opening. Then a week after that, the closed polyps were turning an unhealthy purple color. Latley, only 10 of the original 30 polyps are opening, and as a matter of fact, they aren't opened as full and as much as they did when I first put them in my tank. I will repost with info about my aquarium. Please help

 

My 10g reef is about 2 months old. I cycled it for a month before adding corals. Water parameters are as follows :
Salinity= 1.023 constant
Temp= 76F constant
PH= 8.1
Nitrite= 0
Ammonia= 0
Nitrate= 10 ppm
KH= 9 dKH
Alk= 1.7 milli equaivalents/liter
Phosphate= .5 ppm
Calcium= 440 ppm
Magnesium= 1200-1280 ppm

If more info is needed let me know.
Thanks

 

Some more Info :

10g - 50w 50/50 compact flor. - Penguin 150 power filter - 50w heater - 2 Rio 200 pumps - 20lbs live sand - about 20 lbs Florida aquacultured live rock

Corals and inverts - Ricordia mushroom, sm red and green mushroom rock, sm pink colony poylps, green sand brain, yellow polyps, sm green zoo's, sm candy cane, sm kelp, sm pineapple coral, dwarf green feather duster, sand sifter star, 6 mixed snails, sm unidentified cucumber (live rock bonus)

Fish - 6 line wrasse, yellow watchman goby

 

What kind of lighting and water circulation do you have?
Yellow polyps usually require medium light and circulation.
Personally have never seem them turn purple unless being
covered with something.
Is there any build up of algae,like red slime or detrius on rock ?
Polyps don't like anything on top of them.
Hope this helps

morejongg

 

Sorry , was typing question at same time you
were giving light and water movement info.LOL
Anything picking on polyps or too close to something else.
I've had my green star polyps completely close for up to
three days .Then reopen.

morejongg

 

They are close to the top, 1 inch next to the green zoo's which look great. Some green plant life is growing off the live rock the polyps are sitting on. Water circulation has the polyps moving around very little. Nothing is over the top shading them. They sit about 4 inches under the flow of the filter.

 

None whats so ever. Algae growth is minimal.

 

you could try increasing water flow .Moving rock to another
part of tank to see if makes a difference.
Some yellow polyps require supplemental feeding
along with the light. Plankton,baby brine
Are you adding any trace elements. Since you have a
10 gal tank. Would try only one drop of iodine.
Might want to increase salinity up to 1.025
Something could be picking on it.Do you have any peppermint
shrimp in your tank.
Sometimes we never know why it happens.
Hope I've been of some help.

morejongg

 

Just noticed what you posted on dKH and Alk.
If your dKH is at 9.0 your Alk in meq/L would be 3.20 not 1.7
9.0 is ok but could be higher.
But if your Alk in meq/L really is 1.7 way to low.
I suspect it was a typo though with your PH reading.
If not sure you may want to retest dKH/Alk. and PH.
For what it's worth.

morejongg

 

My numbers are right. About five days ago, my numbers read 8.0 to 8.1 PH, 7dKH, alk 1.7meq/L. I used Seachem's Reef Builder to raise KH and Alk, which changed my KH to 9, but my alk stayed at 1.7. Kinda weird

Should I use a PH buffer to try to get my PH to 8.3?

I also was wondering about iodine and iodide. What is the difference anyway? I can't seem to fine good info and iodine and iodide. I'm not quite sure how to use it either. Info I gathered tells me, iodine is toxic, iodide is good, but yellow polyps need iodine. So what do I do? I bought Seachem's Reef Iodide, but I'm waiting for the test kit to use it. Should I buy some Iodine too? Any suggestions?

I put a peppermint shrimp in around the time they stopped opening. Could the shrimp be the problem? Should I get rid of it?

Thanks for your help!!!