soonerzoo
Reefing newb
I've been testing my nitrates and they have been at about 20 ppm. I've done water changes and use purchased ocean water. I have a true percula, a coral banded shrimp, and 2 anemones ( conys), and some mushroom corals, and about 15 lbs of live rock. It's about 16 gallon aquarium. I'm running a small external hang on the back filter with activated carbon and some filter floss. What could be causing the nitrates? Should I not use an external filter and just use the live rock?