Base of coral receding

[Slickdonkey]

For over a month now the bases of some of my SPS corals have been receding. Check out this picture:

I'm kind of at a loss as to what might be causing this. Water parameters seem fairly normal to me: Alk 12.8 dKH, Ca 440, SG 1.026, Temp 79, NO3 ~3. The tank is 240 gallons (8x2x2') with a 1/2" sandbed. MH's are 4x400W Reeflux 12K mounted about 10" off the water surface.

Corals were doing great for at least 9 months and I'm not sure what went wrong. What's funny is they still seem to be branching and growing.

 

[acrodesiac]

Possible temp., ph, nutrient, salinity swings? I'd like to see a pic of the whole coral.

 

[Slickdonkey]

Possible temp., ph, nutrient, salinity swings? I'd like to see a pic of the whole coral.

Unlikely I think. I have an Aquacontroller and Litermeter (topoff and automatic water changes) to keep these in line. The pH is a little on the low side, 7.8-8.0 during the day. But not the danger zone, I don't think.

Here are some more pics. Sorry, my camera is broken and the shots are off-color and overexposed. But it should give you an idea.

 

[Herefishyfishy]

What are the ages on the bulbs?
Are those red planaria on the dead base?

As a rule, browning or receeding from the base is a lighting problem

 

[Slickdonkey]

What are the ages on the bulbs?

All bulbs are about 6 weeks old. I was having problems before the bulbs were changed as well.

However, now that you mention it I have been having a problem with an algae film on the water surface. Most likely it is hampering the lights.

 

[Herefishyfishy]

If the fresh bulbs don't turn the tide, move them higher or between two lamps with no shading.

 

[acrodesiac]

That does look like a pretty healthy coral other than possibly a little off color. Possibly a water flow issue? So you say nitrates are at ~3ppm? Is that a relaible test result? I'm no master of reef chemistry but I would start with an increase in water changes and skimmer maintinence. Just my 2 cents, good luck dude!

 

[Slickdonkey]

That does look like a pretty healthy coral other than possibly a little off color. Possibly a water flow issue? So you say nitrates are at ~3ppm? Is that a relaible test result? I'm no master of reef chemistry but I would start with an increase in water changes and skimmer maintinence. Just my 2 cents, good luck dude!

Actually the color is fine IMO... the camera is really screwed up. Water flow I don't think is a problem either. My skimmer had gone without cleaning for many months but I took care of that last night, finally. Also I think I'll get rid of my large trigger, should help a bit. Water changes are about 5 gallons/day (automated, I'm not a fanatic). I know more is better but that seems like a reasonable amount to me.

 

[acrodesiac]

However, now that you mention it I have been having a problem with an algae film on the water surface.

Sound like a water flow issue

 

[-=dieseldave=-]

Slickdonkey, you did not post your Mg level and your Alk is too high for me, I shoot for 8.5-9.5 dkh, high Alk usually causes burnt tips however I have seen it cause bleaching and tissue loss on the basses of corals when certain conditions are met. Those conditions are:
Low flow (all most none) across the base.
Using bacterial driven system, like Zeovit, Prodibio, vodka, or sugar.

The second issue could be the flatworms that herefishy pointed out in the first picture there do seem to be flat worms but it I cant be positive from that picture.

The other issue could be the several Vermetid snails, when feeding the can sometime pull unwanted stuff to the coral causing a irritation resulting in tissue recession. I scrape them off when I can.

good luck,
David

 

[Slickdonkey]

Slickdonkey, you did not post your Mg level and your Alk is too high for me, I shoot for 8.5-9.5 dkh, high Alk usually causes burnt tips however I have seen it cause bleaching and tissue loss on the basses of corals when certain conditions are met. Those conditions are:

I will lower the alk a bit. It's a little out of whack because I was fiddling with my reactor recently. My Mg is a little on the low side too; I tested last night and it's around 1190.

Low flow (all most none) across the base.
Using bacterial driven system, like Zeovit, Prodibio, vodka, or sugar.

I don't *think* low flow is a problem. I have a pretty big closed-loop pump and OM 4-way which seems to stir things up pretty good. Ditto on the additives, I don't use them.

The second issue could be the flatworms that herefishy pointed out in the first picture there do seem to be flat worms but it I cant be positive from that picture.

Flatworms? Not sure which post you're referring to. I'm pretty sure I don't have any. I have had them before, treated for them, and haven't seen one since.

The other issue could be the several Vermetid snails, when feeding the can sometime pull unwanted stuff to the coral causing a irritation resulting in tissue recession. I scrape them off when I can.

Ok, that's a new one to me. Not even sure what these look like but I'll see what I can find out.

good luck,
David

Thanks for your help, I appreciate all input.

 

[-=dieseldave=-]

Vermetid snails are the little red tubes around the base or you coral they feed by sending out a mucus web then by pulling the mucus in.

 

[Slickdonkey]

Vermetid snails are the little red tubes around the base or you coral they feed by sending out a mucus web then by pulling the mucus in.

Heyyy... I have seen these. You can even see the little red tubes (sort of) in the first picture. I have seen mucus webs before and wondered what they are.

 

[Slickdonkey]

Oh I see the "flatworms" you guys were referring to. Negative on that, it is some sort of algae.

 

[servo]

As a rule, browning or receeding from the base is a lighting problem

I agree. It looks like the base isn't getting enough light and the coral has died. It isn't flow and nutrient changes wouldn't cause spot necrosis with the remainder of the coral happy and healthy. Flow is more important with larger colonies, while small frags are more light dependent. It isn't likely Acropora eating flatworms in the absence of the remainder of the coral at the base polyps receeded.

IMO/IME the coral will do fine if you just watch it and let it grow.

 

[kevinpo]

Slow tissue recession can be caused by a number of factors either individual or in combination. In your case I would just lower the alkalinity to 8-10 DKh and see if that stops the recession. With a 150 gallon water change a month I would not expect organic compound buildup to be a problem unless you have a very large bio load.

Water flow is the other suspect that often shows up once a tank is past the 1 year mark. This can be due to coral growth, pump output decreasing, and addition of new corals. As pumps age they tend to pump less due to buildup of algae, bacteria, etc.

Regards,
Kevin

 

[Slickdonkey]

Thanks Kevin. The tank is just over a year old now so it may be time to do some of the more unpleasant maintenance tasks and check all the equipment over.

Thanks everyone for your input. I'm going to clear up my algae slick on the water surface, lower the Alk, raise the Mg, scrape off those snails, and clean some equipment.

If that doesn't help, I'll be back.

 

[class clown]

Hey slick - is that by any chance the slimer I gave ya?

as for advice, I can't offer any more than what the other guys have stated here, but good luck.

 

[Slickdonkey]

Yeah Ben that's the one. Growing very nicely until a month ago... well, it's still growing actually. Just not at the base!

 

[tdwyatt]

Phosphate leeching from the rock into the base of the coral.

It could be flow, but from your description, I kinda doubt it. I feel the same on lighting issues, but only if the specimen is overshadowed or has overhangs shading it.

How old is the rock it's on, and is all the rock in your system the same age??? Is this the only specimen doing this on that piece of rock?

The phosphate leaching occurs as the rock's internal circulation of pore water becomes saturated with phosphate as a result of accumuation in a tank with many fishes. Even in systems without flake feeding, this occurs as export cannot keep up with the feeding inputs for the fishes. This is especially true if lots of macroalgae is used to feed the fish and skimming is inadequte. The phosphate will not show up in hobbyist's test kits as the phosphate is bound to the rock when the phosphate in interstitial waters adsorb to the pores of the rock. This will be especially true if you have good circulation in the tank, or if you have reused rock from tanks with a long history of fish in the same system (or poor water change husbandry)...


Just a wild guess.


If the rock is on the substrate, phosphate accumulation wicking is more likely to be the issue, as the sand contributes to the wicking process of phosphate salts and creates a microenvironment where detritus collects in eddies at the rock base. Its decomposition creates nascent free phosphate for adsorption to the CaCO3 of the rock, then as it accumulates in the pores, the production of phosphatASE enzymes by the rock's bacteria gradually release the phosphate from its adsorption sites in the rock pores so it then can be wicked through the phosphate-saturated pore water circulation. Specimens directly adhered to the rock will then aBsorb this pore water through the skeleton (wicking) and the high levels of phosphate then begin to shut down calcification and coral tissue growth from the base up. This is not to say that you don't have some benthic coral parasite that emerges from hiding at night and eats from the base up (unlikely unless you're seeing this condition in multiple specimens in that location), but from your descriptions of the conditions, etc, the phosphate wicking is a likely scenario in a closed system like yours.


HTH