<a href=showthread.php?s=&postid=14923205#post14923205 target=_blank>Originally posted</a> by TX-BJ
How about rigging plastic screen, like is used for crafts. You can buy pretty big pieces & hand sew it together to get the top size you want and then sew side pieces on to hold it over your tank. Another thought is the open weave fabric that is used for lawn chairs, tacked to a simple painted wood frame.
Metal screening would be toxic for your fish if it should end up in the water for any reason. (kids).
Personally I would just buy a glass cover that is made for that tank, $16.99 at Drs. Foster & Smith.