Man those types of gold fish have always creeped me out!
The tank looks good, seem to be on the right path. My goldfish eat all kinds of small leafed plants, I haven't tried glosso in there with them but I do know mine won't eat dwarf hair grass, s Reopens or star grass. But I also always have some sort of vegetable in there for them, right now it's eggplant because I got a bunch for free. I had them in a 55 gallon with probably a couple pounds of duckweed and they ate it all, some of them are so much duckweed their faces turned green lol