I put about 25 of these out, in 5-8’ of water. Primarily for habitat for forage.
PVC sanded with coarse sandpaper, to give better attachment surface the algae
Irrigation tubing
Cinder block on an oiled plywood base to help it set.
Eyelet inserted in middle “divider” w/ concrete apoxy, allows it to be lowered directly into desired location upright
Concrete fills the cinder.
Probably 50lbs, low center of gravity, will not be tipped over
Placed in clusters of 3-5 units
Got the idea from Texas Parks & Wildlife, made some tweaks. Nice because the hooks don’t get hung up like wood.