Radium 20K on M80 with pair of VHO Super Actinics are 750-900 near the top of my rock work about 6" under the water. At 24" deep, I have 400+ nearly everywhere.
14K Phoenix on M80 is 600 at the top of the rockwork, 250-300 in the bottom middle and 200 on the bottom edges.
I imagine that you are 250-350+ down there with those lights... which is more than enough for a slimer.