My fish are fed a minimum of twice a day when the weather
is warm (over 60 air temp average) Now I have heard
that it is not necessary to feed common gold fish but
Koi however, are ravenous and very destructive if not well fed .
I did learn this the hard way after replanting several times
and cleaning up dumped plants. Now keep in mind that Koi are
large, strong fish and small gravel is not heavy enough to keep them from uprooting
your plantings. I like polished river rock. It's heavy enough to prevent problems
and is dark enough to match the dark liner.
If you have the interest, you can train your Koi to eat right from your hand.
Mine like hard boiled egg yolks.