Interesting,
I posted on this thread back in Early 2017 when I had a Colonial Outbreak that made me sick to my stomach. (I was obsessed with getting rid of them).
I Posted this info which shows my dosing Calculations (on my 10 Gal QT) for
@reeferKen 's Question. (may help a bit).
https://www.reef2reef.com/threads/h...-against-hydroids.214950/page-17#post-3727527
Totally forgot about this thread till this post today, because I actually forgot my Hydroids (in my Tank).
As in the post above,
I did treat a few rocks in a small tank for experimental purpose. It killed the hydroids.
The rocks went back in my tank and are still there today (Hydroid Free....or Hydroids Hidden).
I NEVER TREATED MY DISPLAY TANK (2+ Years ago). It looked like this during infestation.
I no longer have any noticeable Hyrdoids (of course I'll probably notice them now...as I look closely). Hopefully not.
This is my tank Today...actually Last week.
My current infestation is (the TURF Algae you see....Green Patches...Never went away since 2016).
I never found way to treat TURF...so I just prune every so often. (Not as ugly as Hydroids)
My other infestation as seen in the current Tank Photo is the Green Button Polyps (Wish I never bought the first one).....But again...I learned to live with them. Same for the Purple mushroom, but they look nicer and I cut them and trade them in.
The point is. You have a living tank and things will grow, spread, since it's all living. SELECT WISELY, and look closely at things you put into tank (yes you won't get everything....Since I also have Aptasia (Free food for Copperband), and Bubble Algae (Free food for Emerald Crab) ).
The 2nd point is, Hydroid Infestations will go away over time (UNDER THE RIGHT CONDITIONS)....
without any treatment, or even without any manual removal. (I still would recommend removing loose rocks and treating or Manual removal which means Carving out hydroid patches from Rock...NOT Plucking, but carving out)...Want extra Insurance (Soak the Rock in fresh water for a few weeks, and bring it back to live in your tank later).
In my experience...over time... (The RIGHT CONDITIONS to "Reduce" Hydroids to an acceptable level) are actually (CONDITIONS....Opposite to what Makes Hyrdoids THRIVE).
I DRASTICALLY CUT DOWN "Broadcast Feeding" of Coral Foods (like Reef Roids, Coral Frenzy, Reef Chilli, etc)
I still feed my corals, but I target feed them, Smaller amounts, and only once every week or two.
All the best to anyone with Hydroids. HATED Them. Still do, but only when they stand out or damage corals.
So with a more mature Tank...You will grow over them, Shade them out, and they might not be an issue.
Treating a whole tank (which I decided not to do), was best decision. More damage can be done treating (I think).