Not over feeding goldfish is a relative term. They are little piggies and always beg for more. Giving them small amounts constantly through the day will make them very happy. When I was home mine always got 5-6 small meals per day.
Indeed, I've heard this; I restrict my feeding to one or two medium-to-large portions a day with fasting sometimes during some weeks...on the days I do water changes, I don't feed for that morning meal after I do the change so the water has some time to "stay clean"...
However, I have also heard and read so many various, conflicting opinions on this subject (as seems to dominate this entire hobby) in that the goldfish should be fed just once per day, NO more and that the "frequent small feedings" as you suggest should be avoided, et al...
If you haven't already start feeding a sinking pellet & mix in some veggies a couple times per week. I grew duckweed when I had the goldy's. They ate it like candy. It does a great job of keeping them from blocking up. I also used to toss in frozen peas directly from the package (still frozen). They loved them as well.
Yes -- right now, I mix up their feedings between Omega One Goldish Flakes (they absolutely prefer flakes) and New Life Spectrum Small Formula Goldfish Pellets. I have seen an improvement in their stool color and growth (I believe) since switching from foods like Tetra and Aqueon to the Omega One and New Life (which I was advised were more premium brands) but the fish seem to go more crazy for the flakes, easily digesting them and not "fighting" over the food like they do in the gravel with the pellets...
I also do feed cooked frozen peas from time to time because the Ryukin suffers from prepetual swim bloat since the day we got him, and the peas definitely make him feel and act better; strangely, he shows no other signs of sickness and is actually growing and thriving in the tank despite his constant recurring bloat. But, yes, we do feed peas from time to time when it seems like he's suffering from the bloat symptoms...
Let me ask this while we're on the topic: Being that my goldfish tend to steer towards flakes,
would it be alright if I fed the New Life Spectrum "General Freshwater" Flakes? I have been told these would be fine for any freshwater species -- including fancy goldfish...
BTW: Anubis & Echinoduras bleherii both do well with goldfish if you want to add a little greenery that won't be eaten.
You mean these would be plants for aesthetic purpose?