Just got a 30 gallon fish tank for a bargain last Tuesday and now I've got 5 platies, 4 cories, a few large snails, a pleco and a molly. I'm planning on adding a few tetras of some kind in a few days too. Very happy with my new tank!

Congrats on the new tank!

Did you cycle it? I'm guessing you didn't since the tank was recently set up and it takes about 4-6 weeks for it to cycle. So you'll want a reliable test kit and you'll want to test the water everyday to make sure the water doesn't become dangerously toxic. If ammonia and nitrites are present you can do a water change to decrease the levels present.

Good luck with your tank!