Bern, consult the wood guy wherever you plan to purchase the wood and confirm that it is the environmentally friendly lumber that they have before you buy. I use it on my ponds.

Treated wood is no longer as harmful to humans because they eliminated arsenic from the formulation, but it still contains copper which is toxic to koi and goldfish. It is more toxic under certain water conditions. Here's a link that explains more. I think I'd look for cedar, cypress or redwood posts instead.

Here is a link that might be useful: copper and koi

Thank you pondmaninal and ccoombs1 for your guidance!
With my painted wood frame carrying a black plastic net finally broken and rotted, I need to replace it in spring with something more permanent to keep herons and leaves out. This is positioned above the water, with only rain water wetting it. I would stain black any wood, being it cedar or pressure treated. My experience with cedar is that it will rot away after 10years as a fence, after 20 years when painted.

I have to look into using composite deck material, that should be lasting forever. Otherwise any of the above when painted should be OK, since rain only occasionally will wash out any copper, especially not when painted.
Thanks again!
Bernd

I have a 2 year old pond (16 x 8ish) that i build up against an overhangin deck and pergola, then I built a bridge over the middle... all out of pressure treated lumber. So a good amount of ptl is over the actual water. I stained the whole thing with a semi transparent stain on the visible surfaces only.

From my overall experience the only issue I had the entire first year was that the algae took a really long time to take hold on anything. I suppose it was a combination of a new pond, so the nitrates would be low and the copper leaching.... And that really isn�t too much of an issue really. From the copper test readings, it never got even close to being a health issue for the fish either.

So I would say, a beam or two would be fine. And painting or adding any sort of sealer will slow the leaching if you are concerned.

nevermore, Thanks for the advice!
Going back to HD and Lowe's I noted that composite decking cut in strips is good to use too. Coming spring I will be able to make a frame for a removable screen.
Bernd

Here is a shot of the pond last fall. We have a 2 year old, so i built a wooden frame over the pond in sections then secured the wire fencing on the underside. Each section hinges up so i can access the pond/plants if needed. And each section is locked down, so no one can get in.

Now this wouldn't be a good method for cranes.. the fence is strong enough to hold a adult up out of the water if needed... so a crane could just walk around picking off the fish through it.

{{gwi:237731}}

Can I use treated timber on the top edge of my koi pond just above water line ?

Nevermore44: I’m designing a pond featuring a deck overhang. I’m curious how you sealed the liner around the deck footings/posts. Thx!

8 years ago! life flies by.

So my set up is actually a cement slab that came with the house.... then I built the pond next to the slab. The liner overhangs and just lays on top of the slab about a foot. Then the deck is raised off the slab in this area only about 2" or so. It overhangs the water... hiding the exposed liner completely.

How far off the water's surface is your deck going to be?