Hey guys and gals, had a quick question for anyone with knowledge. I have 3 ropefish who are typically very active day and night. The last few days one of them started hanging around the top of the tank near the intake tube and heater. As of tonight all three of them are up there. I did a water test moments ago and my parameters are PH 7 Ammonia 0 Nitrite 0 and Nitrates are high at about 40 ppm. The tank is stocked with the 3 ropes, 3 Angles, 6 Skirted Tetras, 4 glass catfish, 1 Bolivian Ram, 1 Bristlenose Pleco, 1 Black ghost knife, 2 African Dwarf frogs, and 4 Rabbit Snails. I have a fluval FX4 do regular maintenance and water changes and also have a aerator. The tank is 120 gal and is not planted. Any and all help is appriciated thank you.