GPU Blocks & Heatsinks
If you are looking to keep your watercooling setup for a long time, it may be worth considering a GPU Block. These can sometimes be known as a 'Core Only' block as the block only covers the GPU on the Graphics card. Whilst this method doesn't usually look as good as a full cover waterblock that is specifically designed to fit the whole board, these core only blocks are ideal for users that swap hardware a lot. If you upgrade your graphics card often, then a Core Only GPU Block is ideal for you. Most GPU Only blocks support multiple graphics cards from AMD and Nvidia.
In addition to a GPU only block, it is also wise to consider memory and VRM heatsinks to cool down the voltage regulators and memory IC chips on the graphics card. These areas get hot when in use and passive heatsinks usually are enough to keep them under control and performing well in your watercooling system