You mentioned doing a saltwater wall tank. Be careful. Very careful. Seawater weighs ~64lbs/cu.ft. For a wall tank, say, 8 ft high, 12 ft long, 3 ft thick, that's 288 cubic feet, that comes to 18,342 pounds, spread over 36 sq ft, giving you 512 lbs/sq ft on your foundation. Make sure your...