These were made for EP01 - Get to Work retail stores. They are retail fridges that you can stock with items and sims will purchase from them autonomously while in your store. They will also keep items, like fish, from spoiling as fast. These also let you attach an aquarium component to them so you can see fish swimming around in it while people are shopping.
Gameplay & Object
Aquarium Retail Fridge
You'll find these items in the Retail section of the catalog if you're on a retail lot. Otherwise you can find them in Surfaces > Displays. This set comes with two pieces, the retail aquarium and the retail aquarium lid.
The retail aquarium tank functions like a retail fridge and is where you can store any fish you want to sell. Sims will come up to the aquarium tank and browse for a while before deciding to purchase stuff from it. You can open it at any time to see what's in it's inventory.
The aquarium lid functions like an actual aquarium, when you put a fish in it's inventory it will show an animated version of that fish swimming around inside. It even has a light you can turn on and off like other aquariums. This lid will slot into the retail aquarium tank so it stays attached. The lid itself only comes in one color but it comes with lots of options to change the decor inside of the tank. Sims will not purchase from this, it's purely decorative but it makes the retail aquarium more realistic.
Note: please be aware you cannot normally store fish in the retail fridge and you'll need my mod HERE to put fish in this object.