I do 25% twice a week, once they are feeding regularly.
I speak from experience.
In the past, I had a mandarin goby I was training onto frozen mysis and a damsel in a small QT tank. Once the goby was eating mysis, I was excited and instead of feeding a couple of mysis a day and sucking it out if he didn't eat it, i began to feed heavily at 15 a day, bascially as much as he could eat to gain weight. Well, less then a week later, I had a massive bacterial bloom due to nutrient build up, and both bit the dust.