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Well it appears I am starting yet ANOTHER thread in the SPS disease section. Pretty soon I will become the leading authority and experience on fighting SPS parasites and diseases. In this months issue we will be covering SEA SPIDERS! noexpression.gif

I had observed sea spiders in my tank several months ago when battling AEFW, my guess is they all came in on the same coral that wasn't properly treated before going into my tank. I did some research and dipped all my corals with Bayer Advanced and I believed all the spiders had disappeared. Once I eliminated AEFW and got my CaRX under control I expected my corals to begin regaining their health and strength back, but unfortunately this did not happen. Instead, I began seeing random spots and areas on my SPS bleach and disappear. It appeared to be STN, but all over the coral in random places.

When there isn't any movement in the tank, that when it's easiest to spot the spiders.So one evening I turned off all the pumps and lights in my aquarium and waited for about an hour and inspected my tank with a flashlight. I was able to see a few spiders on my coral that had been dying the quickest and I was able to observe that where the random spots of dead tissue were, is where the spiders were hanging out on. If you read this article by Dr. Shimek you'll learn that the spider has a probiscus and basically sucks the life out of the coral with it. So I imagine the spiders were either preying on my SPS or they were taking advantage of their weakened health.

One thing I observed was that the spiders weren't only on my SPS, I also found two of them climbing on the glass in my sump. This makes me wonder if they are possibly not species specific parasites, but rather predators with a broad spectrum of food sources to keep them alive. This makes them MUCH more difficult to eradicate since we can't spot treat the tank to get rid of them. Since I couldn't just treat the corals alone like I did with the AEFW, I had to firebomb the entire tank.

I did some experiments on the spiders that I caught with my forceps and was able to kill them with decent success with Kent's Lugol's solution. The smaller spiders would instantly curl up and die while the larger spiders became very lethargic and hardly moved, but appeared to remain alive.



[One thing to note in this topic is that there have been at least two types of predatory spiders observed in this hobby, these and the zoa eating spiders. The zoa eating spiders are much thicker, have larger and hairier legs, and a little bit easier to spot.]

I decided to remove most of the water in the tank along with the fish and hold them in a Brute trash can. I then removed the corals and dipped them in Bayer Advanced followed by one rinse in a clean bucket of water, and a second rinse by pouring clean water over the coral. I then placed the treated corals in the Brute. I left a few gallons of water in the tank along with the live rock and sand and used almost a whole bottle of Lugol's solution. I placed a small power head in the tank for circulation and let it sit for a couple of hours. While this was going on, I took the opportunity to manually remove as much GHA from the rocks as possible. I have a theory that the spiders also prey on pods and the algae was a great breeding ground for pods and could also be why nothing was eating the GHA...


I then removed as much tank water as possible and introduced 20 gallons of fresh salt water to the tank and then reintroduced the corals, fish, and remaining tank water.

The spiders are very small, very thin, and VERY hard to spot, especially when there are other objects in the water, so counting how many were dead in the treatment bucket was next to impossible. I did count many more in the rinse bucket than the treatment bucket. Like AEFW, I believe the spiders aren't killed by the pesticide, but simply temporarily stunned. It is VERY important to physically remove the spiders instead of rest on the assumption that they are dead. The vigorous shaking and rinsing with pouring of water hopefully accomplished this for me.

It's too soon to determine now if the treatment worked, but I'll be monitoring the tank closely for the next weeks to ensure that the spiders were eliminated. If not, I'll be back to the drawing board!

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Here's a video of the movement of the spiders. They tend to move very slowly, but move quickly when they're being chased or when they're floating in the water and trying to grab onto something. This is the type of movement you would be looking for though when trying to spot them.


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Thanks for sharing and good luck! Your hard effort is impressive. My tank has been mysteriously killing sps for years so you've taught me to look for yet another attack vector. Fingers crossed for you.

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Gaaah! Those look creepy. Like some kind of predatory micro robot from the matrix coming to kill you.

Interesting to know about and wow that sounds like a serious pain in the butt.

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Yeah, they're pretty nasty little critters. It's surprising how small they are, yet they still make a *crunch* sound when you squish them against the glass with your finger.

So far I haven't been able to tell it the treatment made a difference. A lot of my SPS have bleached tips, but my alk has been stable for weeks now, so I'm not sure what's causing this.... Still seeing lots of random dead spots on my corals, but I'm hoping that the corals just haven't had time to heal yet.... Hopefully!

Sent from my iPhone using Tapatalk

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  • 1 month later...

I'm happy to report that my efforts to erradict the creatures has been successful! It took a bit of effort, but it's been a month now and I have not seen any trace of them, my corals are coloring up again, and everything is back to normal. I think it's just about safe to say now that the treatment strategy I had was worth it!

I got really frustrated with most threads on sea spiders because everyone talked about finding them and possibly treating them in a certain way, but no one ever reported their outcome and if they were successful or not. Well let me just say that dipping in Bayer Advanced and treating the tank with Lugol's has proven successful! rock.gif

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Perhaps. But I've been hearing rumors that other club members and hobbyists around town have spotted sea spiders in their tanks. If this is true, I can PLEASE PLEASE PLEASE ask that people disclaim that they have seen or may have seen sea spiders in their tank before they bring frags to a frag swap or sell frags or live rock to other members of the club? Fighting these things was incredibly frustrating and no one should have to do it or would ever want to do it.

Do the right thing when trading or selling frags and inform people that there may be sea spiders or AEFW or whatever pest you've seen lately so they can QT the frag and watch extra hard to make sure it isn't introduced into their tank. Let's not be selfish, no one wants to be blindsided.

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