Found another interesting paper on FHM spawning. By Dewitt (1993) in Can Journ Zool V71.
He tried 50, 100, 200 sq cm sized tiles at 25, 50, 100 cm depth.
He found they preferred 100 & 200 sq cm and not 50 sq cm.
They used all 3 depths- no preference noted.
They like to nest next to each other. He theorized that FHM prefer a nest that already has eggs and this leads them to congregate where there are eggs in sight. He cites nests within 4 cm, presumably the edges. Tis interesting as some try to keep nests out of sight of the next nest to minimize energy used to defend. He cites Unger (1983) as finding males nesting near other males also.
So per this paper, make the sites good sized (200 sq cm is 5.6" on a side), put them reasonably close and up to 3' deep.
Saw a BYU paper describing males going out to get a female and lead her back. Apparently it's a rather social thing.
