nalbar--thanks for the good read--it actually helps make my point above with using caulerpa algae:
quoted from Eric Borneman
http://www.reefkeeping.com/issues/2003-12/eb/index.php
"I am not in any way condemning the use of macroalgae in refugia. I am very fond of many of them, although many have quite numerous and toxic secondary metabolites, like soft corals and sponges. In particular, I am very unfond of Caulerpa (Figure 5). It is invasive and very difficult to eradicate. It is toxic to fish and has many metabolites - and releases them when the organism degenerates during spawning. Acidic rhizomes etch carbonate (Figure 6) and these algae can kill other more desirable species by overgrowth. I have had it grow right through the stalks of soft corals. Many aquarists say that it has not been a problem for them. My response? Just wait. It will. I guess my big question regarding Caulerpa is why use it at all when so many more desirable species of macroalgae exist, like Chaetomorpha species, or others (Figures 7 & 8)."