How clean is too clean for a fry tank?

On Mon, 20 Nov 2006 18:17:33 -0600, Köi-Lö wrote:

"Jolly Fisherman" wrote in message
.. .
Then recently I started seeing bulges under parts of the algae sheets.
Not knowing what gas was under it I broke the algae sheet with a
siphon and sucked the gas out. Is this one of the reasons they don't
bother with it? Why wouldn't you use algae or certain nutrient-sponge
plants in fry grow-out tanks?
======================
I raise hundreds of GF and koi fry outdoors each year. I allow the algae to
grow at will. I also keep plants in all the outdoor fry tanks and tubs. See
website below.

Yes and large scale fish farmers grow out their fish in massive
outdoor tanks that cannot be algae wiped constantly either. I would
not attempt to debate that that approach is not viable, especially as
these creatures reproduce quite well in even larger and more
biologically complex environments.

While I appreciate everyone's responses and details of their
experiences what I'm really asking is why small to moderate scale
commercial breeders of many kinds or ornamental fish use such
immaculate and therefore artificial rearing tanks? I would think that
the type of rearing environments you or I or the other posters have
would be preferable.

Just wondering, Koi-Lo, how and where do you sell your fish?