Try using 1 #80 lb. bag of premixed concrete ($ 4 bucks) to make 4 anchors with a simple plastic pan or make your own form with 2 x 4's ( 12" x 12" ), each weighs about 20 pounds. Insert one end of 1/2" pvc stick with a screw through one end into wet concrete, to lock into concrete when it hardens. Glue other end into round sphere, now it will sink easily and will remain where you put it, as concrete anchor will stick in mud on bottom. You can assemble your spheres, with one hole left for anchor stick, and don't glue anchor in until ready to place in lake so you can stack several in boat. Then actual placement is an easy and quick chore, since all you have to do is glue one pvc stick into sphere with anchor attached. Concrete blocks cost about $1.50 each and you have to add tees, and they aren't as secure as using home made concrete anchors. They last a lifetime and do attract and hold fish quickly.
Yes, they are more costly than christmas trees and wood stakes, but when you consider you only have to do the work once, instead of every other year, and all the gas and time you save, they are well worth it. Anglers Unlimited is now installing these type attractors - see their site: www.anglersunlimited.org for pictures of work.
Take a Kid fishing, keep only enough to eat, and release the rest to spawn again. Pop
If you buy the spheres only they are really not that expensive to put out, and they work!! You can carry all the concrete bags and buckets you want, to me time is money. I can put these out in about 5 minutes apiece. I use 1 brick to keep them in place. If you were using them in fast moving water I guess more weight would be necessary. The design and a little weight has kept them from tumbling away.
We have consistently caught more and bigger fish around these attractors. Set them at several different depths for different times of the year.
Good Luck.