I haven't set up the tide movement yet. but when I do I was thinking of having it fluctuate about 3-5 inches, enough for the top of the rocks where the mangroves are to be out of water. I go back and forth with your way of creating the tide. I know it is the best solution and using a smalll 1/2 inch buikhead and black pipe would not be that noticeably especially once the mangroves and macro grow in.Looking good so far. How much is your water level changing??
I totally understand not wanting to take the tank apart. You would only need to drain it to a bit below where your bulkhead will be. Use black or gray PVC so it is less obvious. You could hide the overflow behind the mangroves.