Hi I have a idea to grow the algae on rocks in a SEPARATE container from the opae with extra lighting and water movement and may be a little plant fertilizer, then move to the Opae tank for them to feed on.
A dedicated forum and online store for the Opae ula shrimp!
Sounds like it could work, depends what sort of algae you are wanting to grow. I've just started getting hair algae grow which I believe may of been introduced by my snail addition. It seems to be growing on my heater very well 
