a clown loachs grow to be 12" long, therefore they need at least a 75 gallon tank, and they also need a group of at elast 5, so then you need to bump up the gallonage to at least 180.
bala sharks get big too- 14 inches, and they need ALOT of swimming space, and they like the company of their species also, so then you'd need a tank bigger than 100 gallons.
black ghost knives get even larger; they can easily get to 20 inches or more, so then you'd need a 150 gallon as a specimine tank (by itself) for it to be happy.