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Discussion Starter · #1 ·
Hi!

I am working on a nano planted tank (my journal for background), and in order to keep as much CO2 in the water, without injection, I have a low flow pump (45-96 gph) without surface agitation.

But now I'm worried about oxygen, and circulating "stagnant" water. It just feels like I should be agitating the water to add, I don't know, life to the water?

Is this the thinking of a human that uses lungs to breathe in air?

Once I flooded my dry started tank, the first night I saw plenty of O2 bubbles from my Monte Carlo, since they had been breathing so well. Now that they are underwater, and without CO2 injection, that has stopped. I worry that if I add any livestock in the coming weeks, there will be insufficient O2 in the water.
 

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Hi!

I am working on a nano planted tank (my journal for background), and in order to keep as much CO2 in the water, without injection, I have a low flow pump (45-96 gph) without surface agitation.

But now I'm worried about oxygen, and circulating "stagnant" water. It just feels like I should be agitating the water to add, I don't know, life to the water?

Is this the thinking of a human that uses lungs to breathe in air?

Once I flooded my dry started tank, the first night I saw plenty of O2 bubbles from my Monte Carlo, since they had been breathing so well. Now that they are underwater, and without CO2 injection, that has stopped. I worry that if I add any livestock in the coming weeks, there will be insufficient O2 in the water.
CO2 in your tank is going to be around 2 to 5ppm. You can't 'lock in' more co2 in the water without either a) injecting it via pressurized or diy system, or b) creating it in tank, typically by breakdown of organic matter. Dirt tanks get this with all the things decomposing in the dirt. Those tanks can get as high as 10ppm before lights on. That co2 is used up pretty quickly by plants and it will diminish in a few hours. This is one reason why low tech tanks will typically have at least one lights off period in the middle of the day before the lights come back on in the afternoon/early evening. This allows co2 levels to rise again.

45 gph is the low end of normal for water movement in an 8 gallon tank (if that's the tank we are talking about). Anyway I'm not sure its possible to have insufficient oxygen levels in a planted tank without co2 injection. If you are worried about it just lightly stock.
 

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Discussion Starter · #3 ·
Many thanks! I have the pump on max flow- so around 96 gph. Still fairly low, but I see movement, especially in the Val which is closest to the return nozzle. Creates a nice serene movement.

I will adjust lower if I add chili rasbora and they struggle with the current.

I had not thought of the daytime darkness cycle. I have a Fluval nano light, so I can program the timing. I will definitely try that out!
 

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The daytime “siesta” doesn’t do anything all on its own. If you don’t have an active, fertilized substrate, then your CO2 will never go above 3ish ppm. As @minorhero pointed out, lowering your surface agitation will do nothing to increase your CO2 concentrations, and is dangerous to any wildlife you have in the tank.
 

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Discussion Starter · #5 ·
Thank you all for the suggestions.

I've since adjusted the return nozzle to break the surface to better add oxygen to the water. It was probably fine just on its own with only plants, but once I add shrimp, I want it to be healthier for them.
 
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