D
Dead-pool
, yeah, id go with regular 2x4 over the EMT… u can paint the 2x4 or even wrap them in extra pond liner to keep em from rotting out. Id paint ur whole wood frame anyway to keep it lasting longer. Thats one mistake i made on my last pond build like this. Wet floors made the wood rot out and i tore it down. Structurally it was fine, had to get rid of the black mold tho being indoors. My walls were also hollow.