Digitate Hydroid Explosion

[AndyinAtlanta]

So these little buggers went from, "I wonder what that small white string thing is in my tank." to, "They're everywhere!" very quickly. So I've done some research. First, 100% positive it's digitate hydroids (easy to identify when there's a hundred of them). Second, my main assumption right now is that the explosion is due to overfeeding.

Problem was I have these two cardinalfish that are picky eaters; one especially because it is being bullied by the other cardinalfish (that's a whole different story). They won't eat pellets like my clown fish so I rely on frozen mysis shrimp (which they love). Testing my phosphates the tank (a 30 gal) is around .25, so I'm thinking my overfeeding has led to the spread of the digitate hydroids.

Here's the rub, searching through forums the "solution" vary wildly. Some say it goes away on its own (tank is six months old), some say to use obscure treatments (that may kill a few other things in the process), and others recommend nuking their whole tank.

So a definitely no to nuking the tank, and I'd rather avoid unproven chemical techniques, so does anyone have any advice on what I should do? They appear to be only disrupting one coral (happens to be my most expensive), so nothing is dire. I've stopped feeding my corals reef roids as my understanding is the hydroids are filter feeders. Should I just stick to a better feeding regiment and wait it out?

 

[andrewey]

Can you tell us more about the coral they are disrupting?

I've always been of the opinion that they will go away on their own- that's always been my observation within a year give or take, assuming you're achieving great coraline coverage (they don't seem to grow as well on coraline even in my newer tanks)- I don't know if this is the mechanism, just related, or a red herring and it's simply competition from other organisms around the time of dense coraline coverage (I'm completely in the dark why they go away after a year)?

I've never noticed them bothering any of my softies/LPS/SPS. In fact, I have some growing on the backside skeleton of my montipora digita and they're getting along fine (although the monti is slowly covering the hydroids, so they won't coexist for long).

That isn't to say they can't impact a coral, so I'd love to learn more about your experience!

 

[Jman76]

I had them in my nano pretty bad at one point. I agree with @andrewey they go away on their own, but with reduced feeding. They catch whatever is floating by; they love ReefRoids lol. I cut way back on those and they slowly thinned out. Never killed anything, but made some zoas close up sometimes.

 

[AndyinAtlanta]

Can you tell us more about the coral they are disrupting?

I've always been of the opinion that they will go away on their own- that's always been my observation within a year give or take, assuming you're achieving great coraline coverage (they don't seem to grow as well on coraline even in my newer tanks)- I don't know if this is the mechanism, just related, or a red herring and it's simply competition from other organisms around the time of dense coraline coverage (I'm completely in the dark why they go away after a year)?

I've never noticed them bothering any of my softies/LPS/SPS. In fact, I have some growing on the backside skeleton of my montipora digita and they're getting along fine (although the monti is slowly covering the hydroids, so they won't coexist for long).

That isn't to say they can't impact a coral, so I'd love to learn more about your experience!

Only disrupting my zoa coral. Not injuring or killing, but definitely causing them to close up.

As long as they go away on their own (if I reign in my overfeeding practices) I'm good with waiting it out.

 

[AndyinAtlanta]

I had them in my nano pretty bad at one point. I agree with @andrewey they go away on their own, but with reduced feeding. They catch whatever is floating by; they love ReefRoids lol. I cut way back on those and they slowly thinned out. Never killed anything, but made some zoas close up sometimes.

I think the explosion was due to me broadcast feeding Reefroids one week. Corals loved it, but I think that might have been a root cause for them to spread so aggressively.

 

[Stephanie85]

I think the explosion was due to me broadcast feeding Reefroids one week. Corals loved it, but I think that might have been a root cause for them to spread so aggressively.

Did they ever go away for you? I’ve been noticing them sporadically in my tank but tonight I shined a flashlight in after lights out and they’re everywhere. Tank is about 9 months old. I haven’t noticed them bothering any corals at this point but afraid if they get any worse, they will.