Wow Badflash, that would be neat to see the set up you were describing, with those deep tubes.
What kind of a compressor was he using to pump to 50 feet deep ?...any idea of the air 'volume' he was using ?

Would this help add extra oxygen Badflash ?.....
If you could pump air, into the water return line, just 'after' the pump. The water is under some pressure there....or is this different then the 'pressure' at deeper water depths ?
Maybe it would be so small of a difference, it wouldn't be worth it ?
'Maybe' more so, if the return water was being sent towards the bottom of the tank(s) ?

Here's a link to an interesting article written by Bob Heideman of Aquatic-Eco.
He does mention oxygen levels in different water tempts...
It also, talks about some of the different methods on adding oxygen...and which ones give the most oxygen for the energy being used.

http://web.archive.org/web/200508280627 ... aerate.htm