Overflow question

[Brian Shepard]

Any help with how this overflow works. Use one drain to sump and one for return. Tank and all livestock was given to me without a sump. 120 gallon.

 

[Snoopy 67]

Very difficult to see exactly what's what under blue lighting.

 

[Brian Shepard]

 

[jphilip813]

Can't really make out what we are looking at; if you can take the photos with an orange filter on your phone, that might help out...