I started with 2 nudi's , one is still alive the other I assume(found only half of) went through a power head within the first week. The next week I bought to more. There is atleast two left that I can see possibly still three. I am impressed with them so far . In the month or so I have had them they have kept the bryopsis and hair algae at bay. They have cleaned most areas bare and only the patches I have never seen them around are left. In my case I believe they have worked well but not sure if everyone else will have the same experience. My tank is a 3 foot 65 gallon with about 100 or so pounds of live rock. This is the only two photo I have to show before.
and some taken of the same general area.
Sorry not the best pictures I should of took some to document this before and after but was not thinking.Hope this helps, thanks Chris