there both the same size about 3 inches, well the bass might be a couple centimeters bigger its hard to get a good measurement they never stand still or face the way i need them to lol, its wierd cus they always stay with each other and there is no problem, even hide in same wood, but as soon as im done feeding them the oscar chases the bass like 3 times. right now the oscar eats tuffies, pellets and bloodworms and the bass is on tuffies and blood worms, idk if its cus majority of the tuffies get eating by the bass or what not. I put 3-5 tuffies in at a time if i feed two times a day or i put in 2-3 if i feed 3 times that day, as well as a couple pellets and some blood worms space throughout the day, and the bass usually eats more tuffies and bloodworms than the oscar because he is faster then him. so idk if its because the oscar gets mad cus the bass eats more tuffies or what not.