what type of urchins is that? I almost got a baby blue tuxedo yesterday but instead pick up some Astraea and a Trochus snail to deal with some hair algae. Orphek lens works well to filter out the blue
https://www.amazon.com/gp/product/B07ZJX6JT9/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1