Nice looking pond landscape. Your ecosystem is out of balance though.
Your water is green.

Possible help:

1. You appear to have too many fish for that size pond.
2. You need more plants. Especially submerged oxygenator plants and
floating oxygenators.
3. Consider abandoning the unsightly bottom pump and exposed hose and
going with a Savio skimmer and possibly replacing your waterfall
biofilter to handle more activity.

Paul
www.pondkoi.com