Last Tetre Neon...

Tetre Neon is a kind of fish like 2.5 cm long and small.Bought 10 a month ago and today,the very last Neon is gone to.Its body can't even be found in the tank. So back to normal,the tank is left with a big sucker fish,3 ugly goldfish and 6 pretty goldfish.
Thinking of buying a flower horn in.Will they fight?1 on 9 and sucker fish black and white be the judge?