Good fish for macro grazing?

[Diana]

Hmmm... this stuff is REALLY hard to remove. We have to yank it off the rock, and I get worried about knocking all the rockwork over. We prune it back once a month, and it just comes right back. Its very very thick stuff. I've never had macro that is so tough to get off the rock.

I was thinking of trying a sea hare, is that our best bet? (Its only a 30 gallon tank).

Thanks
-Diana