72 to 80 is probably fine. Like esarkipato says, what's more important is that it is a constant temperature and doesn't fluctuate wildly. I keep mine at 82 constantly (I use the higher temp because I keep Discus). I have 40 Cardinal Tetras, 5 Cory Cats, 5 Otos, 6 SAEs, and a wide variety of plants. Everything does really well and my algae problems are quite minimal. The only plant that I haven't had success with has been the Madagascar Lace (I'm told it just doesn't tolerate the higher temps).