Aquaponics - Venturi adjustment

I thought I'd make a little adjustment to my venturi as suggested by Mike Creuzer in a comment on this post on my Venturi air thing.

He thought I should have some extra bubbles breaking the surface, and it turns out it's a bit of a hot topic in great debate all over the place, but I noticed a very slight oil slick on the surface of the water. I guess lots of things case very slight oil slicks. Eucalyptus leaves for one. Uneaten fish food probably would. I suspect an oil slick - and I'm talking an almost invisible one - would have some effect on gaseous exchange between the atmosphere, and my fish tank's water.

I have no idea if that's true, but I figure it couldn't hurt to stir the surface a little.

So I trimmed the pipe carrying water and bubbles down to the bottom by an inch or so and now lots more bubbles exit.

A 1/4 second exposure shows how much extra water movement on the surface is actually going on.










After only a few seconds there was no more sign of the oil slick.