Yep, Catalina water is what came to my mind when posting in fact -- a lot of people use it is why it would be the best addition IMO
If I still lived in California I'd be using it -- I've recently seen some decent prices on bioassay though and if it really is as close to NSW as they advertise, it might be worth switching over to, but I'm curious to know what disadvantages there may be of using bioassay as well. Good thread