Although your observation is justified... in terms of Construction, your failing to realize that the concrete board is being treated and sealed with the Pond Armour so there is no concern for having the treated wood under it, Since there will be no moisture in the concrete board to begin with (or shouldn't be anyway if all done properly) So the extra cost of pressure treated wood just doesn't make sense to most peoplegreengiant;2759914; said:I Just noticed that most people don't use treated wood against the concrete. in all the construction I have seen they always say to never put untreated wood against concrete but almost all of the DIY tanks have not done this. I'm not knocking anyones method just posting an osbervation. I know you don't want treated wood in the tank as its toxic to the fish but using it against concrete is a great way to prevent rotting from moisture drawn up from it and rotting over time