A 30 gallon/29 gallon tank is WAY too small for either of those fish by itself. The Oscar will need a 75G tank minimum all to itself once it is full grown - they grow over a foot long and are very messy fish. They also grow very quickly if properly cared for, an inch a month or more for around the first year. Even at the current size, I believe you will very soon have bad aggression problems in that small of a tank. So hopefully you already have a bigger tank ready for both fish - otherwise, I agree with Balton, please do your research before buying a living creature.