Hydroids - How do I eliminate- They have taken over my tank

[Mikeneedsahobby]

I have a large crop of these hydroids.

They are through out my tank. I’m thinking of adding corals soon and want them cut back. I know the nuclear option is fenbendazole, but I am going to start by experimenting with peroxide.

trial 1. I pulled a rock out of the tank and squirted 3% h2o2 on it. Result: dead hydroids and lots of dead pods. I was shocked how many pods fell out of it. Pick below is dead hydroid stalks. H2o2 will kill hydroids at full solution strength .

trial 2: pull rock and soak in 1ml/5gal peroxide dip for 30 minutes. 1ml:5 gal is safe for in tank usage. I want to see if this is strong enough to affect hydroids. (I will run this in a couple of days.)

 

[Reefman71]

The top picture looked like polyps? How do you identify hydroids?

 

[Mikeneedsahobby]

The top picture looked like polyps? How do you identify hydroids?

I’m comparing to other pictures I saw. I really can’t identify them myself. They fluoresce green. Seem to like light. But they do close pretty quickly when touched.

 

[Jimmyneptune]

I have a large crop of these hydroids.

They are through out my tank. I’m thinking of adding corals soon and want them cut back. I know the nuclear option is fenbendazole, but I am going to start by experimenting with peroxide.

trial 1. I pulled a rock out of the tank and squirted 3% h2o2 on it. Result: dead hydroids and lots of dead pods. I was shocked how many pods fell out of it. Pick below is dead hydroid stalks. H2o2 will kill hydroids at full solution strength .

trial 2: pull rock and soak in 1ml/5gal peroxide dip for 30 minutes. 1ml:5 gal is safe for in tank usage. I want to see if this is strong enough to affect hydroids. (I will run this in a couple of days.)

I went the nuclear option when I had them.
I started a new system.
I could not get rid of them.
I even used a Benzomatic torch to kill them. It didn't work. it killed them, and they just came back.

 

[Mikeneedsahobby]

I went the nuclear option when I had them.
I started a new system.
I could not get rid of them.
I even used a Benzomatic torch to kill them. It didn't work. it killed them, and they just came back.

That is funny and terrifying at the same time!

 

[Reefman71]

I’m comparing to other pictures I saw. I really can’t identify them myself. They fluoresce green. Seem to like light. But they do close pretty quickly when touched.

How did you get them? I’ve been doing this quite a while and apparently I’ve been really lucky. They look like a total nightmare.

 

[Mikeneedsahobby]

How did you get them? I’ve been doing this quite a while and apparently I’ve been really lucky. They look like a total nightmare.

I bought a used tank and rock about 2 yrs ago. The rock has been in aquariums for 15-20 yrs. I noticed the hydroids right away but they have gotten worse recently. I feed a lot. I’m sure that is why.

 

[Florida Sunshine]

The only way I found to get rid of them is to take the rock out and soak it in a bleach solution and then rinse and leave to completely air dry (several weeks). It kills the rock, but does kill the hydroids.
Cutting back on feeding will help reduce them, but IME nothing eliminates them.

 

[Mikeneedsahobby]

The only way I found to get rid of them is to take the rock out and soak it in a bleach solution and then rinse and leave to completely air dry (several weeks). It kills the rock, but does kill the hydroids.
Cutting back on feeding will help reduce them, but IME nothing eliminates them.

Uhh... certainly not what I wanted to hear. If I can just knock them down enough to get some real estate back for beginner corals I’ll be satisfied.

I ran the second trial.
trial 2: pull rock and soak in 1ml/5gal peroxide dip for 30 minutes. 1ml:5 gal is safe for in tank usage. I want to see if this is strong enough to affect hydroids.
result: the hydroids closed for about an hour then came back out. This failed.

trial 3: dose peroxide at a rate of 1ml/5 gal/hr for 1 week. Maybe prolonged exposure to light peroxide will get them. I know some people that use this procedure to control ick and velvet. Maybe it will fail. Idk. I’ll let you know in a week or so.

 

[Mikeneedsahobby]

I don’t like reading trials without a conclusion. So i am back to share my failure.

everyone else is right. These things are devil spawn.

trial 3 failed. The hydroids were irritated by the peroxide and stayed mostly closed during the first 3 or 4 days. Then they slowly started to open again. After 7 days I notice an improvement but they weren’t dead. After stopping the dosing they came right back. Also the rock I killed in trial 1 sprouted a bunch of new hydroids.

peroxide won’t work for these things.

 

[reefsaver]

For everyone saying replace the rock, it may do nothing in the long run.
You most likely introduced Hydroids into your Reef from buying a Coral or using store aquarium water. Hydroids can be borderline microscopic. The reason I say replacing/cleaning rock will probably do nothing is because Hydroids can grow on the Substrate, on the glass and the stone or rock your Coral is on. I think it would require a full tank overhaul if you wanted to do it without medication. Hydroids won't come off in Coral dip so I think your best bet would be to use dental equipment to examine the Corals and replace all your substrate and live rock.
It sounds crazy to start fresh because of Hydroids though.
I think anyone's best bet is to target feed everything and really investigate a medication so they die out. If you have coral that takes forever to eat, check it and move it to a quarantine tank so you don't have to worry about broadcast feeding the Hydroids. I only noticed the Hydroids a few weeks after I began to stop rinsing my Mysis before feeding.

 

[AcanSkywalker]

How did you get them? I’ve been doing this quite a while and apparently I’ve been really lucky. They look like a total nightmare.

Mine came out of nowhere a year after I started the tank but thankfully they were only on this one rock so I just tossed it!

 

[Sentinel-007]

Have you tried Flabellinopsis iodinea (Spanish Shawl Nudibranch) sea slugs? They prey on hydroids, and on the West Coast, they are the primary defense mechanism in the natural world to control hydroid overpopulation.

 

[EeyoreIsMySpiritAnimal]

Have you tried Flabellinopsis iodinea (Spanish Shawl Nudibranch) sea slugs? They prey on hydroids, and on the West Coast, they are the primary defense mechanism in the natural world to control hydroid overpopulation.

Where can you find these??

 

[Sentinel-007]

Where can you find these??

Try this source: https://www.bluezooaquatics.com/productlist.asp?did=2&cid=83
They don't always have the Spanish Shawl in stock, but they do carry Nudibranchs generally, and can probably help. At least they can let you know when they expect to have Spanish Shawls in stock again, if they don't have them currently.

 

[Puff The Magic DragonSoul]

Try this source: https://www.bluezooaquatics.com/productlist.asp?did=2&cid=83
They don't always have the Spanish Shawl in stock, but they do carry Nudibranchs generally, and can probably help. At least they can let you know when they expect to have Spanish Shawls in stock again, if they don't have them currently.

"Flabellina iodinea preys selectively on the orange polyps of the athecate hydroid Eudendrium ramosum (Engel, 1976; McDonald & Nybakken, 1978; personal observations)."

Not sure if they eat colonial hydroids, per the above article, but hey, worth a shot. I have colonial hydroids, just like OP, and may try one out. They look frikkin' cool too!