Hello All, I'm new to aquaponics and a teacher. I have a small, flood-drain system for my classroom - 70 gallon growbed, 50 gallon tank. It's for educational purposes. There are 10 fish in the tank, ranging between 4-6 inches. My pH (6.0) and nitrates (5ppm) are very low, plants grow a bit and then die off. Any ideas? Do I need to "re-cycle" my system? Forgot to mention, my system is currently…