what types of algae are ottos best at eating?

They like brown algae best. They eat "flat" algae; their sucker mouths aren't
equipped for eating filamentous algae.

do they perhaps eat that course rough algae that loves to grow on glass?

If CAEs and plecos don't eat it, otos probably wouldn't, either. Nothing
really eats that bright green "spot" algae. It's too hard. Though they might
eat it when it's still young and soft (and nearly invsible).

I've found snails to be the best at cleaning glass. But once that spot algae
is old and hard, it's just not very palatable. Get an old credit card and
scrape it.


Leigh

http://www.fortunecity.com/lavender/halloween/881/