I visited your site. Nice info.

Milk crates:

We are using them too in our pond.

We once had a koi get stuck in one (see our website - listed on the
google interface - for pics)

We have left the sides in so that baby fish can hide in there. Seems
to work well. Our lilies jumoed the pots and are now totally entwined
in the milk crates. THAT we had not anticipated! Makes it a big deal
to move them.

Jim