Bristle worms and brittle stars

[Ghost25]

I noticed an interesting phenomenon. In my first tank, the truck was dominated by bristle worms. My second tank started out with a combination of bristle worms and fire worms. But early on I added a piece of live rock from another tank that contained brittle stars and now my live is completely dominated by brittle Stars. I don't have a problem with either and think they are both normal cleanup crew.

But it is interesting that the brittle stars out competed the bristle worms. Anyone have a similar experience? It seems bristle worms are more common, but do brittle stars tend to out compete them or do they just prefer a certain environment?

 

[Nano sapiens]

I had both mini brittle stars and bristle worms together for years and both populations remained quite stable. After a high Mg and Alk episode (with possible metal poisoning from a rusty bolt) I lost all the minis, but now I have a plethora of terebellid worms ('spaghetti worms') which have drastically reduced the bristle worm population.

Have an aquarium running long enough and you're likely to see all kinds of ebb and flow in various populations.