Brown Hydroids

[Coasting]

Yup those are just feather dusters.
You could just glue over the ones that are causing problems but their generally harmless.
Or you could try dosing the tank with PraziPro... Since it kills parasites and worms, one of the reef tank side effects is that feather dusters typically die with its use since they are worms... however don't know if you have other critters in your tank that could be negatively impacted by this.
http://www.hikariusa.com/solutions/healthaid/prazipro/