Which stir bar for best stirring / aeration?

I'm gathering the items for my first attempt at a yeast starter - two liter Erlenmeyer Flask, stirplate, and stir bars. Currently I have three stir bars, a 3/4 inch cross, a 1-3/8 inch square rod, and a 2 inch hexagonal with a raised center. I've posted photos below of the vortex created by each, and was seeking input as to which, if any, would provide better stirring and aeration.

First, the 3/4 inch cross:

This one creates a narrow long vortex which occasionally comes into contact with the stir bar, dispersing small bubbles throughout the water.

Next, the 1-3/8 inch bar:

This one creates a broader, shorter vortex.

Finally, the 2 inch hexagonal:

This one produces the widest, shortest vortex.

So, which one produces better results, length or girth??

any three of those should work just fine, i don't think one will lead to better aeration than another. you just need the yeast to stay in suspension and in contact with the oxygen at the top and sugars in the wort, so a deep vortex isn't needed for the starter just a nice, smooth spin. im not a pro, but this is what i have gathered so far.

Don't get the one with the raised center. I purchased one and I can't keep it centered and it rattles out of place. I prefer the flat stir bars. They can be less tempermental

Dok said:

Don't get the one with the raised center. I purchased one and I can't keep it centered and it rattles out of place. I prefer the flat stir bars. They can be less tempermental

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The raised center works fine with mine, I used really strong magnets.

I'd go with the one that was least likely to fly off center. aside from that, I think with any amount of stir plate induced surface turnover whatsoever, over the timespan of starter wort fermentation, you are probably maintaining a solution of oxygen in your wort that you wouldn't be able to increase without a higher percentage O2 gas than air.

thegerm said:

I'd go with the one that was least likely to fly off center. aside from that, I think with any amount of stir plate induced surface turnover whatsoever, over the timespan of starter wort fermentation, you are probably maintaining a solution of oxygen in your wort that you wouldn't be able to increase without a higher percentage O2 gas than air.

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I used large magnets, and all of the stirrers stay centered.

I prefer using one with the center ring, but only because it works best when I am stirring hot water and Oxiclean to clean up the flask. The ring seems to lift it up a bit out of the Oxiclean solids when it's first starting out.

I agree about the length being irrelevant; the littlest one is just fine for keeping the yeast in suspension - which is the whole point.