Adding O2, increasing O2 levels

[digitalsteve]

ph is 8.0

i have my return line which runs into the tank.... flow is adequate but could be more... there is definately a fair bit of flow in there but it seems to be primarily in specific areas

i have a 3 inch pvc pipe in my sand bed for my morays

im worried there isnt enough flow going past the openings of the tubes thus providing oxygen to the eels.

the fish seem fine , but they swim around whereas the eel stays primarily in his pipe