Help! Something is wrong

[reeferfoxx]

Hi, newbie here. My pagoda cup coral his an abrasion or 'hole' per say. I just noticed this 30 minutes ago. I didn't have time to check the tank yesterday and the day before all seemed okay-ish.

20 gallon mixed reef(almost 9 months established)
23lbs of live rock
20 lbs of sand
Tropic marin pro reef salt
Aquamaxx hob-1 skimmer
Dual jebao rw-4
Reefbreeder LED

Temp: 76.9
Salinity: 34ppt or 1.025
Ph: 8.4
Cal: 420
Alk: 12dkh
Mag: 1350
Phos: 0.09
Ammo: 0
Nitrite: 0
Nitrates 0.7

Last week I noticed zoanthids partially closed. Did some tests and noticed phosphates increased. Closer inspection showed tiny black strings hanging off zoanthid polyps. Immediately pulled the skimmer for cleaning, stirred sand, blew off rocks and did the first water change. That was last friday. Did another water change wednesday. Planned on one more water change this friday or tomorrow. However, I have now noticed that my pagoda looks like something has been eating it.

Fish and invert stocking-

2 Oce. Clowns
1 Helf. firefish
1 red-banded hifin goby
1 Pistol shrimp
1 cleaner shrimp

2 turbo snails
2 astrea snail
2 Nassarius snails
bristleworms and various other critters that would be deemed safe.

So far other corals such as sps(stylophora) and my softies (frogspawn, goni, ricordea) all appear fine. Oh and my Duncan coral looks healthy also.

Please let me know what might be happening! sorry for bad cellphone pic.

 

[Tab28]

Your numbers do not look bad. I have had pagoda cup off any on for years. I have noticed they are very sensitive to sand or other deciduous on them. If it remains on them that area will loose flesh. Unlike other LPS they can not puff out to remove the sand that lands on them. Every day or two i had to use s turkey baster to get off the debris on it. Could something like that be the case.

I will suggest to look your alk to around 8-9. For LPS high alk levels make it harder to absorb nutrients. Your nitrates are already very low for LPS. You can safely raise it to 5 even with SPS. The extra nutrients help their color as well.

 

[reeferfoxx]

You made my day!

Very good to know about my nitrates. I can reduce the alk some. I didn't want to go quite as low as 8, because my future intentions are to have acroporas. To the best of my research, acros wanted a higher amount of alk. I'm not a pro though. Most of this is trial and error. Typically my alk is around 10.5 and 11. I think the recent water changes gave me a higher reading this morning.

The reason you made my day is because ironically I only noticed that spot while blowing sand off my montipora cap! I was thinking how strange it was that my monti cap had sand on it, judging the distance from sand floor to monti cap. The monti cap isn't that much further from the pagoda. Anyway like you said about the sensitivity, that only makes sense. Good, I won't set my alarm for 2am to fish out the culprit!

Since being at work all day, I would say the pagoda has actually improved in appearance. The damaged area hasn't enlarged. But, should I be cautious about the healing process? What is normal healing and not so normal? I agitated the coral with a turkey baster to see the damaged area closer. While looking at it, it appears just slightly pinker maybe with a sort of translucent fuzziness to it. All the polyps are fully extended and don't appear bothered.