I’m aware of a few different ways to make perfectly clear ice, but each has its own tradeoffs.
I’m also aware of a whole bunch of different ways people claim to be able to make clear ice, but I’ve been unable to replicate.
What are you doing? Does it require special equipment? Do you recommend it?
Filtering won’t get dissolved solids like calcium, magnesium, chloride, etc out, and those will all contribute to nucleation of ice crystals. A bunch of little ice crystals is part of how you end up with cloudy ice because it will mess up the directionality of freezing.
I’ve tried using distilled water to combat this, but it isn’t foolproof by itself without doing one of the other methods.
Edit to add: I’ve also tried boiling water to try to degass it, but it didn’t seem to be effective, either.