Hard Corals Receding...

[rwillden]

I added a Kalk Reactor to my system about a month ago that runs only at night. I have some corals that are thriving off it. However, I have a few corals that are not doing so well. I wondered if there’s something I’m missing, or out of place.

My Calcium level is at 505 which I know is a little high, the Alkalinity tested at 2.75 -3.0 meq/L, and my pH is steady at about 8.2

The corals that are doing well are my Colt coral, Toadstool Leathers, Frogspawn/branching hammer, Green Brain, Acropora, Xenia, Galaxia, Mushrooms, and a few others. I also have some green star polyps that are growing like crazy under these conditions.

However, I have a few corals that are not doing so hot: Pagoda, Cup Coral (which are the same type of coral obviously) Plate coral (receding at the mouth,) Flowerpot (which is receding from the bottom up)(I know that flowerpots usually suck anyway.) These are all hard corals with a skeleton of sorts, but I don’t know why they are receding so badly. Any ideas?

Side note: Some other things to consider is that the corals I'm having problems with are not close enough to any other corals to be stung. I have an 80 gallon tank with 2- 250 watt metal halides, and 2- 110 Watt SuperActinic VHO's. It's been up and running for about 2 years with slight modifications/improvements in lighting, etc. over time. The Pagoda and Cup are placed near the top (possible burning???) and the Plate coral and Flower pot are both in the sand at the bottom of the tank (Not enough light?)

Thanks, Ryan Willden

 

[Len]

Plate corals are suscpetible to bacterial infections and that may be why your's is receding from the mouth out (although most of the time it starts at the base). I would also check to make sure shrimps or crabs aren't trying to steal food from the coral's oriface. Plate corals are often victims of these robbers.

Without knowning how your cup and pagoda corals are receding, I can't really suggest why your Turbinaria sp. corals aren't faring well. Like plate corals, it could be an bacterial or protozoan infection (usually distinguishable if you see some "slime" on receding areas). Burning from intense lights - either UV radiation or superoxidation of cells from too high a photosynthesis rate - could also cause damage and explain tissue recession. It wouldn't hurt to move them away from the lights for a bit. Turbinaria sp. do not usually come from shallow waters, and can be found in steep, deep reef slopes. There's a good chance yours are not accustomed to intense lights.

Flowerpots .... well, they just don't live. It is definitely not inadequete lighting since these guys come from turbid waters which recieve little light. The prominent theory of their high captive mortality is depletion of essential elements in closed systems.

All this could be an indication of lack of certain essential trace elements needed to maintain tissue health. I recommend dosing 2 part supplements like B-ionic or C-balance to see if that helps your corals' tissues recover. Water changes is a good idea as well. They would serve two functions: replenish depleted elements as well as dilluting any potential toxins that might be specific to the suffering corals.