About 3 or 4 years ago I jumped through all the TWRA/TVA hoops to find out what the rules were about putting out fish attractors. The final from my inquires was that I didn't really have to have a permit but was cautioned as to where to put these attractors. "Do not put these where anyone diving from a dock could injure themselves if they dived off the dock. Do not put them in any navigation channel of the river or any creek. Make sure that the material that you use is very well secured to the device that you use to sink/hold the structure in place. Do not use any type material which could release any chemicals into the water supply, including old tires".
I use old pallets. I cut them across the boards then use the cut off pieces, nailed onto the 2x4 frame for the upright part of the pallet. That makes a bottom to put rocks or concrete blocks to keep the structure in place. Be sure to wire the weight in place so that they can't come apart and let the pallet float!
I also have a theory about the type of wood. If you think about it do you catch very many fish from pine blowdowns? I don't. So I try to find old pallets which are constructed of hardwood. These will also last longer. The pine deteriorates in a shorter period of time compared to hardwood.
I have made some from PVC pipe also. These take 3 or 4 years to collect enough algae to attract the minnows. Maybe if you took some 60 or 80 grit sandpaper and ruffed up the pipe, taking the shine off it would collect the algae a bit faster.
I did build some bamboo buckets and put these out;
I'll post a couple pictures of the pallet hotels later;