So I have a 30 gal tall tank, it contains two fancy goldfish (one calico fantail and one that's either an orando or just fancy? not sure, but he's orange and fat and beautiful!) & five long tail zebra danio's. So I know my tank is a little over stocked, but I have way more filtration that needed (marineland penguin 350b & tetra ex45), my tank is 100% cycled, and my levels are spot on. Tested today, ammonia is 0, nitrates is below 5 ppm. I didn't test nitrite or ph today, but my ph is usually between 7.6 - 8.0. I wanna stock my tank with one more smaller schools of fish. Can anybody recommend another single fish or smallish species that would be comfortable in a tank with a constant temperature of 72-74 degree's, and would be okay with a possible drop to 70-72 degrees on slight occasion? (only because the ac in my living room is very cold sometimes) If your a "goldfish only with goldfish enthusiast" just save it lol. Also I don't plan on getting while cloud minnows or loaches, and I have cory cats in a community tank and this tank is too high for them anyway.