[African cichlids always have a lack of oxygen, extremely labored breathing]

parameters have been double checked, they are all good. there is a small film on the top, what does this mean?

 

I'll look into getting another air pump for this tank 24/7

 

[African cichlids always have a lack of oxygen, extremely labored breathing]

its 50 gallons with 13 fish, with an aquaclear 110. I find myself constantly putting an airstone in the aquarium because I can tell the fish are suffocating. I usually leave the airstone in there overnight and by morning they are fine. 2 days later they are stressed as heck, won't eat and gasping and yawning like they have no air. anyone know what up? thanks.

 

ammonia  nitrite:0     Nitrate 20

temp: 80

PH: 7.6