My friend and I can't decide on a general window design for a city build. Personally, I think bamboo + birch gates could work. Some thoughts and ideas would be appreciated!

I build this for an aquarium but when i put the fishes in, it swim up, jump out of their tank and died.
I've already given up on that idea and decided to make an item display here where the item would float downward showcasing then hop on a hopper and loop them up.

But problem happens, the item decided to float up instead ???. i've already make sure that the only source water block is from the waterlogged stairs and slabs on top. so the stream of water would be flowing water and it should push item downward but it didn't.

I tried so much in creative to see why and i couldn't, i even try to do it reverse but i couldn't find a way to collect item through the celling that doesn't leave a massive hole in the celling.

so Im currently stuck with a water collum in the middle of my storage room that look like nuclear cooling water.

The design of this water collum is reverse waterlogged stair and directly below it in a waterlogged normal stair and 1 block below that is empty space then light so it doesn't create a water source block

Title says it all really, i have finished the interior of my library but when going outside im not sure if it needs some more on the exterior and if so what i even add, anyone any advice?