Surface Agitation - Enough to keep CO2 loss low and O2 high - The Planted Tank Forum
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post #1 of 6 (permalink) Old 07-31-2011, 04:42 AM Thread Starter
Algae Grower
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Surface Agitation - Enough to keep CO2 loss low and O2 high

I have a spraybar in my tank and every day I am adjusting it so that there is no surface disturbance when the lights are on, and vice versa when the lights go out.

The spraybar is positioned on the left wall so that the current goes across the top length of the tank and circulates back through the bottom and into the intake. (Is this hard to visualize?)

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Anyhow, my question is if there is a sweet spot where there is enough O2 diffusing into the water without gassing off too much CO2?

I have a diy C02 set up, so I am trying to keep as much CO2 in the water as possible.
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post #2 of 6 (permalink) Old 07-31-2011, 05:34 AM
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I would just position your spray bar so that you have a good ripple effect 24/7. This promotes good gas exchange and prevents surface scum from forming. The ripples would be the ones that don't white cap, but just flow as if you had a light fan blowing across the surface of the water.

If you find your CO2 off gassing more than you'd like, perhaps you would need to add an additional bottle of DIY CO2 to your setup to keep the CO2 saturation where you would like it at.

Or you could always just run an air stone on a timer at night to add increased surface agitation / gas exchange during the off hours. Have it turn off 1-3 hours before your lights come on in the morning to get your CO2 levels up to where you like.
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post #3 of 6 (permalink) Old 07-31-2011, 05:35 AM
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With pressurized CO2, I'd say that CO2 is unbelievably cheap, so aerate to your heart's desire (and keep fish healthy and happy) while jacking up the CO2 as high as possible.

With DIY CO2, there's no way you'll gas out your fish unless you're really, really trying to. More O2 in the water column is always good for fish, but you won't hurt them by injecting DIY CO2, so I would suggest not trying to create extra surface agitation until you - inevitably - upgrade to pressurized CO2.

Basically, stop worrying. Set up your DIY CO2, change it out every couple weeks, and keep surface agitation to a minimum. It won't be an issue until you have a cylinder and a regulator.
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post #4 of 6 (permalink) Old 07-31-2011, 06:57 AM
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Agreed. More agitation+more CO2 and you have all the bases covered.

You don't need ocean surf agitation however. You just don't want flat water at the surface.
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post #5 of 6 (permalink) Old 07-31-2011, 07:12 AM Thread Starter
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What happen one time was that I really lowered the spray bar - about 2 or 3 inches below the water level so there was zero agitation, in order to keep all the CO2 from degassing. Long story short, it killed a bunch of my fish not due to high CO2 levels but low O2 levels. And the reason I have come to this conclusion was because I was using a hangen ladder to diffuse CO2 in a 20g tank - barely any harmful CO2 levels. This was also within a week of getting my first canister filter too so I had barely any experience with them. Newbie mistake.

Anyhow, this is were all the worrying is coming from. But I'll try what dBLbogie said. Lowering and raising the spraybar daily has gotten really annoying and what if I forget to raise it one of these days? I am still experimenting with my CO2 set up and recipe for a new tank I got. I am looking at hooking up two 2L bottles and changing one of them every 3 weeks. This should keep a consistent bubble rate, no?

And as for pressurized, I have the money to buy the tank and the set up, but living in NYC left me with no car. And all the shops around here, which are nowhere near me, only exchange tanks and don't refill them. Getting an brand new aluminum tank traded by an old steel one must suck. Plus imagine carrying a 20lb or even a 5lb CO2 tank in the subway. I'll end up tackled by a police guy or a random guy thinking that I am a terrorist.
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post #6 of 6 (permalink) Old 07-31-2011, 08:07 AM
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Don't buy a brand new tank. Enter one of the swap programs at your local welding shop. You get a nice, crappy old, beat up tank from the start, and don't have to worry about inspections, etc..
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