Jikin,
I share my bad experience with a moral of story behind and is very relevant to this topic. I used to keep fishes in 2 ft cement tanks and not able to see my fishes after the water turns green. I am always on a guessing mind as I am not able to judge whether my fishes are sick, alive....it is already too late when I learnt something happen. I can prevent the pest problem but I cannot observe my fishes on whether they are falling sick (unless somebody tell me fishes will never fall sick in this magic water). So, how to sleep well without knowing your precious well being
Though my fishes able to thrive well under GW, I am not able to enjoy it. This really defeat the purpose of having goldfish as a hobby (unless you keep fish for commercial purpose).
Ask ourselves these questions:-
What's the objective of me keeping goldfish?
To enjoy seeing them or not seeing them.
Is GW the only method to produce nice goldfish? (Yes/No)
If your answer is Yes, then why others can produce equivalent nice goldfish.
If your answer is No, then why take the suffering of not able to appreciate your fishes 24/7?
Again this goes down to very basic fundamental of the objective of this hobby:-
Goldfish Appreciation!