I'm trying to find some macro algae that can survive the brackish conditions. I've heard of people using Chaeto with their Opae Ula ,is it the same as Chaetomorpha Chaeto sold as a Algae Marine Nitrate Reducer?
The chaeto that you use in marine sumps may survive a small while in brackish water but will die off eventually. I had no such luck with it, hair algae will survive brackish water but if you don't keep an eye on it the stuff can start taking over the tank.
They sell the macro algae that would survive in brackish water in the US but i haven't found any over this side of the pond unfortunately.