Howdy, and allow me to be the first to actually welcome you to this board.
I would like to apologize for the many rude (well-intended, but rude) posts above. I will make sure to clean this thread up for you, so that you can use it as a reference for your science class, rather than a case study for a psychology class.
You got a project assigned, came up with a proposal, and now you came to MFK to get feedback, which is great. Especially for your focus on predatory fish in a good size tank, there is no better source of knowledge on the web.
Let us inspire you. Obviously, a 125 gal tank has lots of potential. And while your project is limited in time, let's also plan ahead to build a predatory community that lasts for a while. Absolutely possible! I'd split it into two subprojects: Setup and stocking.
You've got a tank, you need a filter. Anything you're leaning towards? This also depends on your budget.
Now, let's talk fish. You already named a few, just elaborate on your decision-making, interests, preferences, and I am sure folks here will provide you with productive feedback and suggestions.
At the end, this is your project. But we're happy to have you visit our site and talk fish with you.
HarleyK