digitate hydroids

[YHSublime]

I have what appears to be digitate hydroids in my tank. 

 

Every morning when the lights are off, there are long white stalks, almost tentacles, that come off my rocks and coral. During the day, they are gone again. 

 

There seems to be a lot of misinformation on them, and I'm wondering if any of our members have experience, or actual scientific knowledge of:

 

1.) If they are harmful 

2.) If there is a way to get rid of them if they are harmful

3.) If they will in fact just die out on their own. 

 

Based on what I've found, here is what I'm putting together:

 

They are fairly common in new tanks, and also hard to keep alive, and will end up depleting organically. 

 

Here's the misinformation I think I've found:

 

They pack a powerful sting, and will leave you with welts, sting your fish, and also out compete your SPS (Not LPS, surprisingly...) They will multiply very quickly, and there is no getting rid of them. 

 

Thanks in advance for any conversation or help!

 

[FirstContact]

Not sure if I’m using the right screen name, but “ squishie” had hydroids in her 90g and reported they were extremely difficult to get rid of and basically over grew everything. She tore down the tank and sold it and started over with a new tank.

[Origami]

Hydroids are fairly common in new tanks. Many times they starve out in a few weeks or months. The one's I've seen more typically are the kind that appear on your glass in the early days of setting up a new tank. Some hydrozoans can pack a powerful punch. These tend to be the larger ones that can hit you with a lot of stinging cells at once. Chances are you're seeing the kind that look like threads "fishing" in the water column. There's no guarantee that they'll disappear - especially if there's food to be found in the water column. However, most of the time they do. You can try to wait it out (starving them) or, if a more aggressive approach is wanted, then siphoning them out when you see them. Alternatively, you could try hitting them with a little kalk paste to encourage their demise. 

[menglish]

I think brown/blue clove polyps are in the same family of hydroids.

Here is a long thread on R2R about riding your tank of hydroids using fenbendazole, a problem that is also developing in my tank.

 

https://www.reef2reef.com/threads/eliminating-blue-clove-polyps-with-fenbendazole.308994/

[Neto]

I dont know if these are the same but I had colonial hydroids that go in a tube if you touch them and they where absolute cancer. Nothing kills them and they sting like crazy. I got rid of them because my tank crashed and I lost all my corals. 

[YHSublime]

Hydroids are fairly common in new tanks. Many times they starve out in a few weeks or months. The one's I've seen more typically are the kind that appear on your glass in the early days of setting up a new tank. Some hydrozoans can pack a powerful punch. These tend to be the larger ones that can hit you with a lot of stinging cells at once. Chances are you're seeing the kind that look like threads "fishing" in the water column. There's no guarantee that they'll disappear - especially if there's food to be found in the water column. However, most of the time they do. You can try to wait it out (starving them) or, if a more aggressive approach is wanted, then siphoning them out when you see them. Alternatively, you could try hitting them with a little kalk paste to encourage their demise.

The stringy fishing kind, yep. And only when the lights are out. I’ll play this out I guess, clean up the tank a bit should help.

 

 

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[John Ford]

*USE AT YOUR OWN RISK*

 

Interceptor for dogs will take care of that type of hydroid. It will also kill all pods and most inverts so use with caution~  

[rt502]

2-3 years ago I sold my cbb and one spot rabbitfish to a reefer here who specifically wanted to get rid of these hydroids and was about to break down his tank out of frustration. The cbb wiped them out. Not sure if this is an option given the size of your tank.

[YHSublime]

*USE AT YOUR OWN RISK*

 

Interceptor for dogs will take care of that type of hydroid. It will also kill all pods and most inverts so use with caution~  

 

Ah. I've got a lot of pods and life that I'm kinda keen on. I might go down this road if it doesn't work out. I really didn't notice them till the other day, only during lights out. They look like this

 

2-3 years ago I sold my cbb and one spot rabbitfish to a reefer here who specifically wanted to get rid of these hydroids and was about to break down his tank out of frustration. The cbb wiped them out. Not sure if this is an option given the size of your tank.

 

I would do a temporary one, but the problem is CBB's are hard enough in a tank the size for them. And I've got a lot of zoanthids I'd be worried about. 

[BAJAB]

They will sting and irritate your zoas to death. Bigger polyp palys can withstand it but the smaller polyps will close up and eventually melt. I had them in the past and they did not just go away on their own and stayed for over 4 awful years. They are the worst pest IMO. The ONLY thing that went after them at all (and with vengeance) were the almighty copperband butterfly. They hunted them down almost exclusively and 90% were gone within two days. I watched them go from one digitate hydroid to another. It was so satisfying to see. But of course copperbands are very difficult to keep so that presented another issue. If you do consider copperbands, make sure you pick ones that appear to like searching and hunting the substrates.