So, how do you get rid of them?
Back in november last year I had NO3 level at 40 (I tried hard to make a copperband to eat, so I flooded the tank with food). This was the period when those spiroids went crazy and took over the tank. I had to scrap the back glass every week because was fully covered with white dots. Same on rocks (but those I didn't cleaned) - even large snails I have became covered with them. Sump, pumps, even inside skimmer - I had them everywhere.
After poor copperband died (by starvation as didnt eat anything) I started to work hard to reduce the NO3 levels. Beginning of January I finally get NO3 to 0.00 and since then I keep it at 0.25-0.50 (for corals, to have some food :) ).
Weekly glass cleaning was needed every other week, now I have already 4 weeks since I didnt clean out the back window and didnt saw any white dot on it (it is a black window, so very easy to see them). Also on rocks I see coraline overgrow those shells, so I presume are dead.
As I read around about any type of hydroids, the best way to get rid of them is to starve them - no miracle solution in a bottle. I think mine entered the system on snails, but once tank went crazy they just took advantage of this.
I think that will always be some of them alive in my tank just waiting for next mistake, but as tank is more and more stable, they have less chances to beat me :p
I am not an advanced aquarist, nor a science geek - this is my experience and I dont claim is the only way, so others may have different opinions.
