start to my diy 480 gallon timber pond (not finished)

8'x4'x2'
it is only half way up in this pic.
i have 1/2" all thread rod and lock nuts and washers for the corners and middle.
im going to put plywood on the inside.
then a layer of styro board,then pond liner.
going to filter with 2 55gallon drums and a uv sterilizer.
media as follows,cut up pvc,scrubbies,sponges,filter fiber,felt.
not sure on what gph pump to use on this,suggestions?
will update as soon as i get more done.

its for misc. fish and my koi.
4x4s cost more then these,these were 3 bucks a piece.

it is officially 8'x4'x2'
i used 16-8' pieces.
is the class ready for step 2?
step 2 is drilling 54 holes. lol