oxygen levels

[Avi]

I've been having problems with fish health in a 110-gallon FOWLR. The symptoms don't appear to be disease related...at least, they aren't observably parasitic...cloudy eyes, faded coloration, face downward, hiding, loss of ability to eat and even see...ended by inevitable death. The fish I've lost are mostly angels and butterflies. Wrasses seem to be completely resistant. In any event, when it was suggested to me that it might be oxygen-related, I tested and the results are 5 mg/L which seems to be considered "low safe." It could be that the angels and butterflyfish are high in the oxygen-demanding catagory. What can I do to increase oxygen levels in the tank? I have a sump with a good chaeto growth and plenty of flow. THANKS.

 

[DiverD]

I would shoot for 7 mg/L. I didn't see your circulation listed. Is it by chance low on the gph? Your skimmer outlet should be saturated, but is that oxygenated water making it around the bottom of the tank. Interesting...

 

[greenbean36191]

5 mg/L is well within the safe limits for reef fish and several times the lethal limit. These symptoms also do not match a typical case of hypoxia.