You can create price alert here, copy coupons and view price history. Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Brand Descriptive Geometry DESGEO, Capacity 1.5L, Model C300, Color White, Product size 203mm*102mm*254mm, Voltage 5v, Power 5w, Product material ABS /PMMA
Banggood
Banggood warehouse is located in China. There is one great coupon!
Link: Banggood product page
1. ($54.59): Cuponation9
you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGaab9d4, MVC8SPRING, 8wEbgaInS5, BGJUNEGSG9, 9OFFSUMMER
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – Descriptive Geometry DESGEO 1.5L Fish C300 Aquarium [EU] ($-3)
Price history and price alert
Price history (for all/most countries) for Descriptive Geometry DESGEO 1.5L Fish C300 Aquarium is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).
. There’s only 1 record in my database, so I have no idea if the price is OK. One coupon is available. Cool!