I'm looking into using pressure treated wood, like the Douglas fir from Home Depot or Lowes, for a project over my koi pond. I've heard mixed things—some say it's toxic for fish, while others have mentioned that the newer types of pressure treated wood are now safe due to changes in the treatment process. Can anyone clarify if this is true, and does it apply to all the new pressure treated lumber sold at places like Home Depot or Lowes?
2 Answers
I wouldn't recommend using pressure treated wood at all for anything in contact with your pond. Most treatments still contain copper or arsenic, just in different formulations. Even though some wood meant to be submerged gets a heavy-duty treatment, regular pressure treated lumber might not be safe, especially for fish.
That's a good question! First, could you share more about how you plan to use the wood? If it’s for an above-ground frame, you might still need a pond liner to protect the water. But if it’s going directly over the pond, I can see why you’re concerned about chemicals leaking in.
Yeah, I should have been clearer. The pond is already built, and I'm thinking about making a small bridge over it with the pressure treated wood. Since it’ll be over the water, I worry about any chemicals leaching in from rain or sprinklers.
But I heard arsenic was phased out in residential lumber around 2003 or 2004, and now it mostly contains copper. I guess it could still affect algae and microorganisms, but it’s probably safer than before.