There are two types of pressure treated wood. One is called womanized, and the other is a cupric (Copper)pressure treated. One is basically like a creosote pressure treatment like used with telephone poles and the other, which is supposed to be for gardens, is pressure treated with a copper preparation. You definitely do not want water from evaporation dripping off of the copper treated into a sump or refugium. Also if it is womanized the petroleum products will not be great introduced into a tank. I personally would not replace the materials , but I would put a couple coats of spar varnish over the wood and silicone caulk the seams between the framing materials and the covering materials. If it is copper treated the galvanized straps used at your joints are going to suffer from galvanic action as copper and galvanizing materials do not mix. The nails and screws used with copper treated wood should be stainless steel so as to inhibit reaction with copper as much as possible. The second choice in nails and screws are plastic (resin) coated. Hopefully that is brownish grey wood and not green tinted (copper). :frustrat: All will be OK after coating with Spar Varnish, or lots of urethane. And silicone. Think natural wood in the future, no pressure treated, no pressed board and if possible no plywood unless it is marine plywood or at least plywood with resicorinal glue. IE CDX (exterior) rather than AC (interior). Otherwise it means sealing all surfaces real well, or pray for a lack of condensation, splashes, evaporation and leaks. :grumble: