I had my oscar in a 40 for 3 years with an eel, and some 4 and 5" african, as well as a MOno that was 7" and a 5" male Convict with two females.. that was interesting

.. In the last two months I've put him in a fifty five. All I could afford.. Read my signature... THreee years in a forty... I just bought a 150 2 days ago. If I were you I wouldn't waste my money on a 125 if you want a 180.. The sooner the better is not going to save you money or help you get your 180 SOONER... If you want the 180.. your seventy five will be just fine for quite a while with such small fish.
Personal preference is the factor here... If you want the facts... All our fish live in river or lake or the ocean. Nothing you buy will be big enough.. SO get the one you want. Not the one that's going to make you wait longer to get the one you want.
unless you want 240 or more then you might want to buy something now LOL.
I cannot waiit to get my 150 up.. But I am buying a house in the next 30 days so I kinda need to... DOn't want to be taking down a 55,40, and a 150.....