Losing corals to RTN!!!!

[apedroza]

In the last couple of days I lost a couple of small frags to RTN. I tested my water and everything seemed okay.

Nitrates 0ppm
Phosphates 0ppm
salinity 1.022
ph 8.3
calcium 550ppm
alkalinity7dkh

I did a 10% water change just to cover my bases but yesterday on of my larger colonies started showing signs of RTN. I quickly fragged off the dying pieces in hopes of saving it. Does anybody have any ideas on what I could do to stop this??? Any suggetsions would be greatly appreciated.

[Bill S]

Could just be "small frags"...

[apedroza]

Yeah that's what I thought, but most of the frags Ive had for a while and were showing excellent growth. But the I had a big colony of A. prostrata that I had to quickly cut because some of the branches started showing signs of rtn. It looked okay this morningso hopefully it will make it.

[hobogato]

how sure are you about that salinity. 1.022 is pretty low, and if your measuring device is a little off, it may be even lower.

[erikharrison]

ok im lost... what is RTN?

[apedroza]

I'm maybe 90% sure its accurate I use a refractometer. What is a normal level for salinity? I have always kept it between 1.022 and 1.023.
Also is the fact that my calcium is high and my alkalinity is around 7dkh a factor. Iam trying to get my alkalinity to 9dkh.

[hobogato]

Rapid Tissue Necrosis

when was the last time you calibrated your refracto? i think that your calcium/alk is a little out of balance, but i dont think it is bad enought to cause RTN. i would also try to get that balance a little better. have you checked in the middle of the night for those little starfish? i know i have found them around the base of frags that showed recession before.

[apedroza]

I haven't seen any of the starfish (and when I do I take them out immediately), but I have seen hermit crabs all over the corals, but not just the ones that are rtn. They are on the healthy looking ones as well. Is this a problem?

[erikharrison]

Ace, is there an easy way to calibrate refractos?

[cpreefguy]

they come with calibration water

[alton]

Sounds like a broken record but how old is your lamps? When everything else is perfect. That's what happened to me.

[Texreefer]

I'm going with the low salinity.. and if there was an event that caused it to drop really fast, that would be an issue.. it get the salinity up as a preventative anyway

[apedroza]

Okay I will try raising the salinity.

[hobogato]

i calibrate mine with RO/DI from my filter.

[caferacermike]

I've had a few go unannounced like that in the past. No particular reason why and yet the remaining pieces all look fine. I've often wondered if substances shed from creatures like zoa or leathers get released into the water and the smaller frags show the issue to a greater extent. Lost a Turaki that was growing like crazy this way. One day it looked great, 4 hours later/skeleton. Hope the rest of the tank pulls through. You are welcome to any frags that I might have that you lose to replace with.

[Bill S]

Are your bigger corals doing OK? Like Mike said, sometimes they just don't make it. Few reefers like to admit that they've lost corals, especially frags. But it happens. Probably more often than everyone thinks. For instance, I got a couple of "colonies" from Ace, that when he was doing his AEFW treatment, he didn't have spots for. He recommended that I frag the entire colony, and not keep any of the base rock. I did this, with 6-12 frags of each one, on a new rock. Only about 2/3 of the individual frags survived the first week. They are now growing well!

[apedroza]

I think I found the culprit. I noticed that the frags that were dieing were near the output from the sump. I cleaned the pump today and found part of a sandsifting star stuck in the intake filter of the pump. Could this have caused it? All of my big colonies except for the prostrata are doing good. The prostrata has not shown any more signs of rtn either.

[aprilmayjune]

I don't have any SPS but I've heard even a little piece of sand (or starfish) that gets blown onto the SPS colony can start RTN OR STN. Just my two cents.

[matt]

Ace, is there an easy way to calibrate refractos?

Unfortunately, calibrating refractometers with R.O. water almost ensures that they will read seawater at the wrong salinity. I had no idea about this until I read a lengthy article by Randy Holmes-Farley about refractometers and measuring salinity. The oversimplified bottom line is, all refractometers that we use in the hobby are designed to measure the salinity of straight NaCl, which is not what seawater is. Most refractometers will read seawater approx 1.5PPT high if they're "accurate" for what they were designed for. So, if you want 35PPT, you could try adjusting your salinity so that your calibrated refractometer reads 36.5PPT and supposedly you'll be fairly close.

There are two easy solutions to this; one is to calibrate your refractometer using pinpoint 53ms conductivity probe calibration fluid; this has been tested to be accurately at 35PPT, so you put a drop of that on your refractometer and turn the screw until it reads 35PPT. At this point it will NOT read zero with R.O. water, but that's what the experts say to do....

Another option is to spend a few bucks and get a decent, lab quality floating glass hydrometer and thermometer, and use it and a temp correction table to really accurately measure your specific gravity. Tropic Marin make one that is supposed to be really accurate.

[Bill S]

Hmm. I've been using high quality floating hydometers for years... uh.. over 35 years!

[Richard]

I just ordered a refractometer. I've been using the same crappy swing arm hydrometer for 10 years or more. Now I'll probably start having problems.

You might consider getting an orp monitor. Really useful thing to track on your tank and can tell you when something bad is going on with your overall water quality.

[addboy]

Another vote for salinity.

[apedroza]

Well I haven't lost any more colonies and I raised my salinity to 1.025 (is this an OK level?) over the last 3 days. I was gone yesterday and most of today and when I came home all my sps looked fantastic, but my zoas were acting weired. Many of my zoa colonies were closed and looked a little shriveled. Should I be worried? I check my levels again and everthing looked good,and I did a small water change just to be sure. I am also noticing my small hermits crawling ll over the zoas that arent opening up. Should I be worried about this??

[matt]

If you used a refractometer to measure your specific gravity at 1.025, it's probably closer to 1.0235, or around 31PPT. Still 4PPT under average NSW levels.

Getting back to RTN, I've had two frags of the same colony in different parts of my tank; one thrived, the other died of RTN. I've never been able to figure why some frags succomb and others don't. With your zoas, maybe the hermits you saw had recently crawled over them, causing them to close.

[caferacermike]

Anthony I'm not sure what you were running your SPG at before but I was always told to run at .025-26 with a reef tank. .020-22 for fish only. I've read that online, in magazines, and was told very similar from the shop that set me up. Of course I check mine with a coralife swinghydrometer that is probably older than I am, I was headed out this week to buy a refractometer but not I'm questioning if it's worth it, so who knows what I'm really at. With daily evaps I've noticed my SPG climb all the way to .028 with no ill effects. If I forget or am not home on day 2, makeup water day, and add 4g on day 3 I make sure to do slower than normal so as not to cause a large drop of salinity quickly.

[apedroza]

Well I have both types to measure SG. But they both read differently. Which one is more reliable??

[matt]

When you say both types, I guess you're referring to the plastic swing arm and a refractometer? The ugly truth is that neither one is probably accurate. If you're really interested in knowing exactly what your salinity is, you have to bite the bullet and either calibrate your refractometer with the pinpoint conductivity calibration fluid (it must be the pinpoint stuff; that's been tested and is known to work for this application) or get a tropic marin or other lab grade large glass floating hydrometer.

You could take a chance that your refractometer acts as most of them do and assume that it's reading .015 high on the SG scale, meaning if it shows 1.0265, it really means your SG is 1.025. But, that's just a guess. On several threads on RC, people are posting that their refractometers are off by as much as 5pts; that's like reading 1.025 and having your SG be 1.020. I'm going to get the pinpoint solution and calibrate mine sometime soon.

[apedroza]

Where do you get the solution??

[JimD]

I have an Oceanic swingarm and a refracometer, they both read the same. On the other hand, my old Deep 6 was significantly off.

[Bill S]

The problem with ALL of the above EXCEPT the glass hydrometer, you never REALLY know if it's working right! I've heard of folks losing lots of livestock from the swing arm hydrometers. I have TWO of the large glass ones. They are the ONLY kind I trust. But, then again, I've been using them for 35 years.

[caferacermike]

I was having troubles with the batteries always going dead in my digi thermometer so I bought a little glass thermometer and hydrometer built together. It was about $9, I wonder how accurate it really is.

[SoLiD]

I'm going to look for some of that pin point salinity calabration solution and find out how far off my refractometer is. I hope it's not that bad.

[apedroza]

Well my swing arm read 1.0235 and my refract reads 1.025. When I read with RO/DI water and it reads 0. Not sure which one is correct or what else I can use to calibrate the refract?

[JimD]

http://reefkeeping.com/issues/2006-12/rhf/index.php#11