Poor oxygenation in AIOs?

[guyute1500]

I'm getting back into reef keeping with an old eco mini 28, I'll start a build thread when i actually get water in it. While "researching" these forums the issue of poor oxygen levels in AIO tanks came up several times, usually with sick fish. I plan on running a jebao dep- 2000 with a VCA rfg and a jebao MLW-10 in the display. Chaeto in the fuge will be on a reverse cycle and the tank will have a screen top. Any reason I should be concerned about oxygen levels or transfer?

 

[Garf]

Any reason I should be concerned about oxygen levels

Not if you've got plenty of circulation

 

[christinna77]

I think the problem comes down to:
- not enough surface agitation
- closed tops
- people turning their powerheads down at night because they think the fish need to "rest", but it's actually the opposite. Keep them running because algae and other photosynthetic organisms stop producing oxygen at night but continue consuming it.

Good surface agitation for gas exchange is critical, just having good circulation won't cut it. I point both my return nozzle and powerhead up, as well as like to run a skimmer even on my AIO nano tank (don't need to collect if your nutrients are low).

 

[Fish Fan]

I like to run my AIO's so that in the rear filter section, one chamber cascades down into the next chamber. This helps increase gas exchange in AIO's.

 

[Garf]

I like to run my AIO's so that in the rear filter section, one chamber cascades down into the next chamber. This helps increase gas exchange in AIO's.

I've spent some effort in testing oxygen in my skimmerless tank just with a cascade from tank to sump and lots of in tank flow. I have never detected low oxygen, for what it's worth.

 

[Aqua Ultraviolet]

In an AIO, oxygenation is usually more about gas exchange than simply water movement. Keeping the surface gently agitated, maintaining good circulation, and allowing some air exposure in the rear chambers can help. I’d also keep flow running overnight, since oxygen can drop when photosynthesis stops.