Am I a asshole for telling my girlfriend that we are absolutely not getting another aquarium set up and she needs to either get a refund for the aquarium she ordered or sell it. We already have a 20 gallon long in our room with shrimp and some tetras and we are currently cycling a 100 gallon in the living room. She just spent $400 on a 200 gallon aquarium and stand wanting to add another one to our livingroom. we had kinda talked about getting another one a hour before but it was my understanding that we'd rather not have to remove our TV and entertainment center into the storage. She surprised me a few mins ago by saying "hey (petname) I got us a new tank ordered" at first I got a little audible irritated and told me let me see the listing to make sure we have the space in the guest bedroom assuming she meant just a small one to make that room pop. When she showed me what it actually was I got a little more irritated letting out a sigh. She of course was disappointed that I was irritated with her. Then I sat her down and tried my best to explain that even if we had the space for another tank that big that we couldn't afford to keep it going (tanks get pretty expensive with water and electricity bills.)  I'll admit I got a little loud slightly above "inside voices" if you remember that from school lol. And demanded that she get a refund or sell it when it arrives. This obviously made her upset we both said some shit that we didn't mean. For example I said "well maybe if I didn't buy you your necklace and ring I could afford to keep it going" (recently got engaged I proposed using a ring and necklace) she came back with "maybe if you didn't buy your motorcycle money wouldn't be tight right now" Which is unfair in my opinion considering I traded my previous car to the seller of the bike so I only had to pay $150 for the bike. 

TLDR my girlfriend made a substantial purchase behind my back after we barely talked about it, I demanded she either got a refund or sold it. Things where said that weren't meant. This is really weighing on my mind. 