Yes that appears to be the only spot. It is a 115 gallon tank. His tankmates are a Picasso trigger, clown, yellow tang, yellow tail damsel, 6 line wrasse, and a small snowflake eel. It is a live rock tank with live sand and fan worms. The tank has a hand on overflow with sump and protein skimmer. The protein skimmer is a small crappy hang on one that i received with the tank and am saving up to upgrade. My guess for high nitrates is possible over feeding and lack of a good clean up crew? Not positive as I am very new to the hobby I have only had the tank around 3 months so any advice/opinions is greatly appreciated!