Underwater tank spider?

Bobhelp4 · Feb 10, 2019

Can someone help me determine what this is?? It looks like a small underwater spider

DSC reef · Feb 10, 2019

Looks like a zoanthid eating spider Remove asap

Lovemyreef2015 · Feb 10, 2019

+1^^ very clear picture for a ID

cracker · Feb 10, 2019

That thing is creepy ! Get rid of it if possible!

Bobhelp4 · Feb 11, 2019

DSC reef said:
Looks like a zoanthid eating spider Remove asap

I removed it ASAP after I took the pics just because I was not sure but if there is one are there more??? What could I do to get rid of them? I have noticed some of my zoa colonies depleting slowly while most of my others are flourishing. Could this be because of the spiders?

Bobhelp4 · Feb 11, 2019

Lovemyreef2015 said:
+1^^ very clear picture for a ID

Thank you! Any idea how I can get rid of them? I assume if I have one I have more...

DSC reef · Feb 11, 2019

You could try dipping your colonies. It's a possibility there are more.

Retro Reefer · Feb 11, 2019

I would agree with DSC reef.. remove and dip your Zoa’s, If you have one spider chances are good there are more of them.

Maacc · Feb 11, 2019

DSC reef said:
Looks like a zoanthid eating spider Remove asap

DSC totally right here, kill them with fire (beyer)

tankstudy · Feb 11, 2019

Bobhelp4 said:
Thank you! Any idea how I can get rid of them? I assume if I have one I have more...

From what I have seen in the past, if you have a lot of poor looking colonies and you find an adult, you probably have far more than you can actually see. The juveniles for the spiders are very small.

I've used a few methods in the past with some amount of success.

You'll want to treat the whole tank but if your concerned, you can just treat the individual frags outside the tank but this will require multiple treatments. Not to mention you'll need to treat all your soft corals and anything that is mainly soft tissue. The spiders can target more than just zoanthids, depending on species, and their are a lot of them. For example, I had spiders that targeted rock flower anemones and zoas/palys.

The drug of choice is milbemycin oxime. It may or may not work, keep in mind that there are many species of spiders and some may be resilient to this drug. You can only get this pill, sentinel, from a vet with prescription. However, you can now buy it in a liquid form called Dr. G's Coral Dip. Although the bottle says not to dump it in to your tank directly, it's just milbemycin oxime and people have been using that directly in their tank for many years. I've also directly used it in my systems but all tanks are different so think about it carefully first. It will kill more than just spiders, it will wipe out your pods, worms and other smaller lifeforms as well which can cause a terrible chain reaction. We know for a fact that wiping out a ton of flatworms can kill off your tank inhabitants from the toxins released by the dead flatworms and this drug appears to take out some species of flatworms as well, so think about it carefully first.

The direct in tank dosage I've seen over the years is about 1-4 mL per gallon. Remove all carbon rock and turn off your skimmer. I usually treat for about 3-4 days and then return the carbon rock and skimmer.

Outside the tank dosage for dipping, 1 bottle of Dr. G's makes about 2 gallons worth of dip if I'm not mistaken. I don't have the bottle on hand so I can't say for sure.

Do not use other classes of this drug like Ivermectin. Ivermectin is much easier to obtain, especially the 1% solution for cattle. It's super powerful and will kill more than just the spiders, corals and fish will die. There isn't a known safe dosage for other drugs in the same class yet. I wouldn't mind trying to find out thru my own experimentation but I no longer have any spiders and spare coral to experiment on.

Coral Rx and other similar dipping treatments are generally not enough to kill the spiders. Most are actually too weak and by the time you get the concentration high enough to kill the spiders, it's pretty toxic to everything else.

Good Luck, spiders are my worst enemy in this hobby.