Advice needed after using fenbendazole in reef tank / food

[skr791346]

Noticed one of my fish showing white stringy poo, even after going through 3 weeks of General Cure soaked food in quarantine. Fish was already in display so I decided to soak food in fenbendazole and feed. (Ratio was 1 scoop of fenbendazole : 1 scoop of Focus : 1 tablespoon of frozen food)

I repeated the treatment for 3 days. By day 3, I noticed all my xenia, cespitularia and GSP closing up. Day 2, most xenia have melted away and my nepthea colonies are looking droopy, starting to shrivel up. Lost two of my linkia starfish, frogspawn and GSP completely browned out and closed.

I was running carbon, UV and skimmer the entire time. I was aware that people used fenbendazole to treat xenia, gsp and hydroids but I was using such a small amount, didn't realize it was going to still have such a huge impact...

After doing a 100% water change, spread out over the course of four days, nepthea colonies and GSP looking worse.

After doing research on it, I came across this quote re: longevity of fenbendazole in another thread.
"Apparently it does not breakdown well in water. It is insoluble and bacteria don't break it down readily. I have not seen any studies on it outside the digestive tract of animals.
Top seahorse breeders who use it ,advise ; rock and substrate exposed to it is to be considered unsafe for reef tank use indefinitely."

Do I need to start considering changing all rocks and sand out? What are my options? I would like to reintroduce softies back into the tank at some point. Most zoanthids, goniopora and mushrooms seem ok so far.

When doing fenbendazole baths on fish, I recall leaving the bath water sitting for about 5 days after removing fish because I just didn't have enough time to clean it up and it was still cloudy

 

[Seawitch]

I looked it up and found another seahorse site that said it was risky to use in a reef tank. It's chemically similar to praziquantel except for the addition of a sulphur atom. I found a study that praziquantel degrades quickly in a mature reef tank, but I don't know if fenbendazole would. I would wait at least a couple of weeks before trying to introduce anything back into the tank. Then try one thing, and see how it does before adding anything else. And maybe do another water change in a week.

 

[Florida Sunshine]

I used it to treat my tank for hydroids and had removed all inverts as advised. The only thing other than the hydroids that I lost was my gorgonian. After about a month, I put the inverts back in and they were fine. This leads me to believe it does go away or become less toxic or whatever. I even got a new frag of the gorgonian and it is doing great about 3 months post tank treatment. On the fenbendazole thread I was following it talked about taking out GSP and Xenia so those aren't a surprise really, but I didn't know it was a problem for nepthia since I don't have any and don't remember it being mentioned in the threads I read.
More water changes and some time and I think you will be fine with softies again.

 

[Lucie]

I confirm, DON T USE FENBENDAZOLE IN A REEF TANK.
Most inverts, copepods and corals will die. Rocks and sand will leach it after the treatment , depending on dosing.
When i use it (mostly for hydroids and NEVER in DT), i then bleach everything that was in contact, even the glass tank.
The only thing you can do now is to change your rocks and your substrate, and pray for your corals in QT...

 

[skr791346]

Thank you for the replies guys...I'm really hoping I don't have to replace all rocks and substrate but I will if need be. I'll give it a few months and try a frag of Xenia to see how it does.

@Florida Sunshine May I ask how big your overall system is and how much fenbendazole you dosed? Did you do anything in addition to water changes after treatment?

@Lucie Luckily, most of corals & inverts are still alive including snails, shrimps and hermits. It was just a few specific species that seem affected. How would bleaching get rid of the medication if it's insoluble on surface?