With some DIYs, these scratches and can be removed using a surface polishing compound. You can use various kinds including automotive scratch removers. We recommend the following:
These 2 brands are easy to find both online and in retail stores
Meguiar's (G10307) SCRATCHX (online or retail store)
NuFinish Scratch Doctor (online and retail)
This one is available online
Novus 2 Plastic Fine Scratch Remover (online)
You don't have to completely remove all the scratches. The down-lighting from the unit will hide most of the scratches.
Steps
We use "NuFinish Scratch Remover" since it is quite easy to find in the retail stores. We recommend that you remove the tank from the assembly to make buffing easier.
1. Apply the compound generously with a sponge and start buffing with some pressure
Important: Be sure to support the back (front) side while you buff
2. Use dry microfiber cloth and continue to buff it clean
3. Repeat 2 - 3 times and it should remove most scratches
Do not use alcohol to clean the tank as it can ruin the coating on the acrylic.