Any idea on what this is?

[echo53775]

What are these white things on the macro algae. They are also on some clove polyps.

 

[Spare time]

Hydroids

 

[echo53775]

Any idea if this is harmless kind? I saw some posts say they can go away on it's own and some say they can be problematic.

 

[Spare time]

Any idea if this is harmless kind? I saw some posts say they can go away on it's own and some say they can be problematic.

They can sting corals but as to whether they go away or not I am not sure. They always seemed steady in my tanks.

 

[Srfnhooker]

Any idea if this is harmless kind? I saw some posts say they can go away on it's own and some say they can be problematic.

I've had them. Killed some with h2o2 on rock I could remove. Eventually went away on their own. I limited feeding as someone suggested. Haven't seen any in 6 months or so. Good luck.

 

[echo53775]

was it undiluted h2o2? I tried diluted dip for 5 minutes but I am unsure if it'll work. I'll observe for now. Thanks.

 

[Srfnhooker]

was it undiluted h2o2? I tried diluted dip for 5 minutes but I am unsure if it'll work. I'll observe for now. Thanks.

Straight 3%. No diluting. Lucky for me it was on the side of a smaller island rock so I just stuck that side of the rock in the h2o2 for a few minutes and then used a toothbrush. Had them show up in other places that I could not use the same technique. Reduced feeding to once a day and only what the fish would eat in a couple minutes. I've stuck with that approach. I don't have anthias or the like so this works for me.