400 gallon project

[untamed]

Originally Posted by BC564

From the second pic...it would appear your urchin is getting quite big or very close in the foreground.

Yes, that hatpin urchin is probably 10" in diametre. When I got HIM, he was maybe 2". There are two urchins in the tank. One hitchiked in on the LR. The hitchiker urchin is smaller, with generally shorter spines. That one has grown from <1" to about 3". Both eat coraline.

There is a display of Bengaii Cardinal Fish with Hatpin urchins at the Vancouver Aquarium. The young Cardinals are supposed to hide in the urchin spines, but I saw no evidence of that in the display. None of their urchins were as large as mine, and they are clearly the same species.