Only other similarly disabled fancies should be put with bubble eyes. This means other bubble eyes or celestial eyed goldfish. Other types will outcompete them for food and will usually stress them out with their activity level. Bettas shouldn't be mixed with goldfish at all, they are tropical fish and need a heater. They do best at 78-80 F and goldfish cannot tolerate water that warm. Also, a 10 gallon is too small for even one goldfish. Fancy goldfish like your bubble eye need at least 20 gallons for the first fish and 10 more gallons for every goldfish added after, and common goldfish need 55 for the first fish and something like 20-30 for every additional common goldfish. Common goldfish (feeder goldfish, common goldfish, comets, and shubunkins) are much better suited for life in a pond. These are messy fish that can grow to be huge. Fancy goldfish can get to be nearly a foot long and pretty big around, and common type goldfish can get even bigger.