Get out the old CD's and an orbital sander? Scuff them up with 36-60 grit, paint 'em with epoxy paint, some PVC tube larger than the center hole, cut it into donuts. Use a threaded rod and nuts/washers to make stacks of CD's???

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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).