An easier tank

Hey guys just wanted to let you know I will start out with a much smaller tank i was thinking 300 gallon custom tank from my aquarium store, I will use a life reef filter and some good temperature controller. My combination will be a tiger oscar, fire eel and black ghost knife fish will that combo work. Im making room and my room for it I know im getting it just need to know when anyways I thought about what you guys said and I think its ridicoulous to star out with such a large tank with experienced fish so ill start smaller and easier to enjoy the hobby. Ps any good tips from experts on a good PH level and KH level and temperature I was thinking 75 degrees still working out the PH and KH.

I know I have experience with my uncles 180 gallon tank full of trout and sucker fish and a gar I helped take care of it when I was little. I know its a big commitment but I know I truly am into predatory fish and understand the commitment.

Thanks axs377 guys my plamn is to start off wioth my uncles 80 gallon tanks since he needed the money he sold the 180 gallon tank awhile ago so ill use the 80 gallon tank for the baby fish in the 80 gallon tank then move the it out once its an adult into the 300 gallon tank. Will that strategy work?

Ok thanks Eclipse390.

Well I have pics of his 80 gallon tank somewhere on a computer so I shall find them, I think he used powerheads if im correct I do remember he had a filter and a secondary filter. All the fish have sadly passed away do to old age but I will probably get his 80 gallon tank also he built his own custom stand which is pretty cool.