Cories don't go well with goldies and cichlids.
Rams, checkerboards, apistos, discus, angels, festivums, kribs, etc.

Cories don't go well with goldies and cichlids.
do a school 05 like 15 rummy nose tetras, some shrimp and a snail, with live plants and a dark substrate, itll look nice
If it's a 20 long, like a 36" tank, you could get a Leopard Ctenopoma. It's a kind of Gourami from Africa. I have one in my 30 and he's easily my favorite fish. They get to about 5" and they're great at feeding time. They curl up their tail like a leaf and stalk their prey. Great fish.
But in only 20 gallons of water, it would be iffy, you would have to filter the crap out of the tank and do 50% water changes every week.