plant?

i think it's Amphiroa beauvoisii Lamouroux. that's really impressive K+. i would have never found that.
so it's not dangerous then. thanks a lot.

 

i just did some more reading on this. from i read i think it's a form of coralline algae. is this true? how would it spread? is this beneficial to the tank in any way?

 

yep a coralline algae. like all algae, you can make cuttings of it and propagate it that way, exactly the same as you would do if it were coral, or it will spread on its own through sporolation, more commonly referred to as "going sexual". The spores settle and you get more coralline. Like all algae, coralline algae absorbs nitrates and phosphates, in the case of coralline, it will absorbs calcium too, as well as other elements like magnesium for example. (iron too etc...) As a slow grower though that is made up of mostly calcium, it won't filter much, but the big benefit is that it is cool, and looks great. (Also very difficult to keep alive and growing in aquaria, that is some nice stuff you got there).