How much surface movement is enough?

D

Dark Rose

Feeder Fish
MFK Member
Mar 27, 2013
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United States
I still seem to be confused about this topic... I've got a 75g with African Cichlids (Haps, Peacocks, Mbuna) and just want to be sure they've got enough oxygen...

I've never been able to find a clear answer on how much surface movement is enough...
I've got a spray bar on my canister, and a Fluval (I believe, at work now) wave maker fan thing... I've got good surface ripples, but not really any agitation where I see air bubbles being introduced... Is just seeing ripples and current on the surface enough, or do I need something that agitates it more or introduces air more, such as a powerhead or something?
Also, the spray bar and wave maker are both on the same end of the tank, directing current towards the opposite end where the filter intake is... Should I have the spray bar and wave maker on opposite ends? I read somewhere about more "circular" current...

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Drstrangelove

Drstrangelove

Potamotrygon
MFK Member
Oct 21, 2012
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San Francisco
The purpose of agitation is to get water with low oxygen to the surface where gas exchange occurs. Moving water (which is saturated with oxygen) around the top of of the water column is not an effective way to provide oxygen to water at the bottom of the water column.

However, if the filters are pulling water directly from the bottom of the tank (inlets are at the bottom) and dumping it to the top, that's a solid way. If there is an air stone in the tank at the bottom it will reduce water density causing the water from the bottom to rise. A power head can pull water from the bottom as well. All of these methods work. You just want to look to see how water at the bottom is being routinely brought to the top.

The 'correct' amount is what ever provides a fairly reasonable amount of oxygen throughout the tank. Almost all the gas exchange is at the top, so moving water up and down is crucial.
 
D

Dark Rose

Feeder Fish
MFK Member
Mar 27, 2013
443
0
0
United States
Ok...
Looking from the front of the tank, my spray bar is on the right side top, half of it pointed slightly down, half pointed level or slightly up... the wave maker is forward of that, on the same wall, also pointed slightly up...
I have 3D background siliconed in place about 2.5" out from the back wall, with 2" diameter holes covered in mesh, about 2" up from the sand level, one towards each end, one close to the center. The filter intake is behind the background, lower left side. So all three "intake" holes for the water are low, and the actual intake itself is also low, opposite side from where the water is incoming... which is high.
So from what you've described, it sounds like my setup should work pretty well?
Also do a 40-50% water change at least once a week, if that is relative to anything.

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