Layne, there is a fine distinction between structure added to attract larger fish and the type of cover need to protect fingerlings. They serve slightly different roles. One popular method of providing cover is by submerging pine trees other folks have submerged wooden pallets. Different species of fish like different types of cover. Hang on for a more expert opinion (which I'm not).

Here is some good reading for you. Archive thread about structure and cover.

It will take you a while to read all of that but it is a great primer and should give you some ideas as to what other folks have done.

JHAP
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"My mind is a raging torrent, flooded with rivulets of thought cascading into a waterfall of creative alternatives."
...Hedley Lamarr (that's Hedley not Hedy)