You dont need to use pressure treated wood, I assume you dont want the canopy to rot but if you vent it or make it open top than it will never rot and if you paint the inside and poly coat it then it will really really never rot.
Also wanted to mention to you to consider selling any fish you have that grow to be large and focus on fish that can make good use of the 150 cube for many years to come.
At least for me, the fish is what kills me and pushed me to change tanks 3 times. In a year or so I am probably going to sell or give away the tangs that are outgrowing the tank and focus on reef fish that dont grow as quickly or to be as large as some of the fish I have.
Also wanted to mention to you to consider selling any fish you have that grow to be large and focus on fish that can make good use of the 150 cube for many years to come.
At least for me, the fish is what kills me and pushed me to change tanks 3 times. In a year or so I am probably going to sell or give away the tangs that are outgrowing the tank and focus on reef fish that dont grow as quickly or to be as large as some of the fish I have.