Pond Boss Forums POND CONSTRUCTION Creating habitat Rot resistant wood.

Sunken cover will last much longer if the right species of wood is chosen. Here in the midwest, there are a few trees that produce wood that can last a very long time.
Top on the list is probably Osage Orange, which is also good because it grows low and has lots of branches. Black Locust has been used for fence posts and lasts forever. It does not have many branches, but grows straight & tall. Mulberry grows low and densely branched, and is very common along telephone lines and in urban areas where it is often a weed tree. White Oak was used for building ships, if that says anything. They have rounded leaves, not pointed like Red & Black which rot quickly. Eastern Red Cedar can be great, if the tree is large enough. It is the heartwood (of any tree)that has the high resistance and lasts a long time under water. Of course aerating the water will likely shorten the life of underwater wood, but that is a reasonable tradeoff. A last note to mention is that rot resistant woods are among the very best for firewood . . . so heat solar, and sink your trees!

what is your opinion of artificial cover, like PVC ?

Be sure to use sand paper or a light grinding wheel on the pvc. Scruffing it up helps algae , plants etc to be able to grow on its surface.

I have red oak that has been in the water 20 years and is still sound , white oak also.

My personal opinion on plastic and such is that the bottom of a pond or lake is a far better resting place than a landfill. The plus for plastic is that {out of reach of UV rays}, it will likely outlast wood. Minus is that it would attract fewer organisms that support the food chain{than wood}, even when plastic is roughed up (which was a great idea).
Remember, wood lasts longer in the absence of oxygen . . . which we always want to increase{oxygen levels}. Plastic would not be effected by this much.
Bottom line, I prefer wood with it's benefits . . . but plastic is also a good use of waste scraps.