I have 2 urchins in my 120 they keep the coralline in check. My coralline grows pretty fast though.
Its all they eat in my tank.
I would wait until you have the back wall covered before introduction.
Urchins eat tons of coralline. And lots of it. This pane of glass on my tank was covered top to bottom with coralline, and you couldn’t see through it. Within 4 days, my rock urchin cleared almost all of it. I did purposely move the urchin there to clean that pane. But do not underestimate how much coralline an urchin eats.
Ok, so now I have this BT urchin in a tank without much coralline. What are my options? Can I use sheet algae? Will my clowns try to eat it off the urchin?
I would say pieces of nori are probably your best option. Maybe try cutting the pieces small enough so the fish can’t get it when the urchin covers it. But my long spine urchin pretty much lives off chaeto, so that is an option if you have any available.
Well, long story... I have 3 tanks in my system. 180, 75 and 40 fuge. 75 is my first tank tank and I still keep it online. There isn’t much more than live rock and chaeto in it. But it also houses my long spine urchin. So I have chaeto in my 75 growing during the day, and chaeto in my fuge growing at night. The long spine just got too big for my 180, so he has been banished to the 75. Counter intuitive, I know, but it’s about the size of a basketball with spines. So nothing in my 75 eats chaeto except my urchin. If you have tangs or other herbivores in your tank, then chaeto would be a difficult option. I was just mentioning that my urchin really likes chaeto so it is an option if you don’t mind keeping some of it in your main tank.
Those should not eat chaeto. If you do grow it in your main tank and your fuge is running counter to daylight, then you get the nutrient removal benefit all day long. As well as potentially feeding hour urchin. But that is personal preference, if you don’t mind looking at chaeto in your display tank.