Oxygen flow...

[zurus]

Hi All, i've got a new 90 gallon tank with a Eheim 2317 and a 2215....do you think this will produce enough oxygen in the tank? I haven't put any fish in yet as I am still cycling but it seems like the "flow" isn't as much as my 45 gallon, which is what the fish are used to.

[Aquaviewer]

The dimensions of your tank are important to determining your water circulation and oxygen exchange, with surface area being one of the important factors (temperature, plants etc also contribute to DO levels).  A tall and narrow tank will typically have more of an issue with maintaining good gas exchange than a long low or wide tank (this is proportional to the size of your tank).  Filters don't actually produce oxygen, the movement created by the intake and outflow of your filters help to circulate the water (I'm assuming you already have them on full) and promote gas exchange. 

If you are cycling and want to do a quick test of your flow patterns you could try and drop a bit of slow sinking fish food or powdered flakes and see how it moves around the tank.  If the sinking particles don't appear to fully disperse about the tank you can adjust the angle of your outflows, add spray bars, or powerheads to help agitate the surface or create more of a rolling action and current, particularly if your fish like a lot of movement.

[zurus]

now that the fish are in the tank it appears that there is enough oxygen for them as they love their new home. The only thing I am wondering about now is when I put the flake food in, most of it stays at the top unless I create some waves to bring it down.. is there anything I can get to put at water level to create some kind of current at the top? I hope I am making sense here...

[cory]

as it gets waterlogged it should sink. At least my flakes do.