I added about 15L of fresh RODI water and washed some dirty looking salt build up back into the sump. No other urchins in my tank.
Within about 15 minutes of the above, the urchin started broadcast spawning.
Just finished doing a bit of a clean up in the sump and my Echinometra mathaei started it's broadcast spawning. Ten minutes of "broadcasting". Looks pretty tired now. Just sitting there, very relaxed :thumbsup:
Anyway, I have a short video of the sequence if others are interested in watching: