H. Erectus appropriate setup

Good day all,

I have a few questions about my set up before I bring in some new ponies into my life. The setup in question is a 60g cube (24x24x24) that is plumbed into my 150 gallon reef, and down into the sump. The cube is set up as a display refugium that I am hoping to keep some horses in, but I am unsure if it is adequate, as I have never kept horses before.

The whole system runs at 72° and the cube’s inhabitants are some green star polyps, 4 various gorgonians and a pretty healthy bed of caulerpa. There are a couple of scarlet hermit crabs and trochus snails for clean up and a small power head in the corner that has a slow pulse, just to keep things moving. Does this sound like it would be alright for the chosen species? If so, how many would you recommend starting with? I was looking at the 6 smalls you guys offer but fear that ultimately the tank will be too small. I am happy to email pictures of the setup if you need them as well. Any help is greatly appreciated!