Without vegetation you will have no reproduction from shiners, and survival of any offspring from any fish will stand close to zero chance of survival due to lack of cover/habitat.

You may need to consider thinning out your GC and Koi if your goal is to establish a self sustaining forage base. You will not have one without some kind of habitat whether it's vegetation or artificial [trees or pvc].

Many men go fishing all of their lives without knowing that it is not fish they are after. ~ Henry David Thoreau

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