JR if you not rich then please reconsider. My 75 gal reef has 1 gallon a day evaporation I do 10% water change weekly that 15 gallons a week on a 75 gallon. I have to make the ro/di water or buy it. fresh is 50cents a gallon and sw is 80 at the lfs. Do the match even a 300 gallon is going to cost a bundle to maintain. Not to mention sand, pumps, back up pumps, salt, carbon , uv sterlizer, lights. Dude it gets crazy expensive and even the electricity can overwhelm you. I just set up a 175 for fowlr I have 2 tangs in it and have about 4000 dollars invested. This hobby is crazy expensive and it takes a tone of time and dedication. Again I think you are a good kid you have just been mislead somewhere down the road. Keep your dreams start a little smaller and get some more experience and you will be thankful in the end.
Think about this. What are you going to do when the black tip dies from starvation or from temp spike or just from stress alone. I am almost 30 years old and I would cry for the fish and for the money. Go to the Shed look at the big sharks and keep you passion it will pay off one day. Start smaller