Haha sounds like my experience, but with a larger tank! When I first got my AR380 we had 8 neons, 8 silvertips and a rainbow shark. I've had gouramis, platys, swordtails over the last few.. none of which survived. So I can't laugh at your stupidity.. because its my stupidity too!
Best thing I did was get a test kit, it tests for pH, high pH, Nitrates, Nitrites, and ammonia. I also got the gh & kh kit too and only just figured out how to use it last night.