Since the iguanas eat at least once per day, and the fish / turtles eat at least twice per day, I had to make the feeding access easy and accessible. I didn't want to have to go outside into the yard in order to feed them. It was a challenge, as the screened in pool was a 'separate' barrier from the cage with its wire material. I wound up making an opening in the screen enclosure, by cutting into the screening, and putting in new segments of aluminum supports.
Originally I was going to make the door hinged, but this seemed it would always be getting in the way. I decided to just make it totally removable. There are only 2 barrel bolts that need to be undone, so it is a quick and easy process.
The bottom of the access door, where they would be most likely to push, has a thick piece of aluminum angle iron, so that the door cannot be pushed out. The top, of course, has the barrel bolts. If you are going in there to throw some food to the fish, you can just swing the door forward; or you can take it out entirely.
The door is a bit wider than the proposed iguana house, so we will have access to both the house (which is where we intend to feed them), as well as throwing food into the pond, for the turtles and fish.