I never have 0 nitrates! Suddenly thats the case. I have had a bag of De-nitrate in return pump for a month. 17 gal Fluval tank. Cycled for over 4 months. Has multiple plants, 1 large sailfin blenny, 2 small clowns, 1 small acro, 1 Waving Hand Anthilia, (2 1/2 " when open), couple of snails and crabs, 2 peppermint shrimp, live rock, live sand. All have been thriving and still look happy! Having a little hair algae, but otherwise great. Checked ammonia and was a little. I never have ammonia! No nitrite. Getting new test kit. Dosed with Stresscoat and removed the de-nitrate Could it be causing the issue?