Surface Agitation???? - The Planted Tank Forum
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post #1 of 7 (permalink) Old 10-16-2015, 05:19 AM Thread Starter
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Talking Surface Agitation????

My LFS recently told me that I'd have a bit of a problem with my CO2 injection if I didn't figure out a way to minimise surface agitation caused my wet dry filter...
I thought it could be fixed by raising the water level to just above the filter outake level...
Does anybody know if doing this will solve the problem?
What exactly classifies as a goodly amount of surface agitation??
Why do we need it (or a lack of it)??
And, does a wet/dry filter impact Co2 levels in the water negatively?
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post #2 of 7 (permalink) Old 10-16-2015, 04:04 PM
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Surface Movement

Hello Jir...

If you're used to doing large, weekly water changes, then a filtering system with a gph (gallon per hour) rating of roughly 4 times the size of the tank in gallons will be enough to mix oxygen into the tank water. The large weekly water change will also help keep the tank aerated and give the fish a healthy oxygen level.

Filters that move a lot of water will drive off some of the carbon dioxide, but there's enough in the surrounding air and from the dissolved fish and plant waste to keep the plants healthy.


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post #3 of 7 (permalink) Old 10-16-2015, 04:10 PM
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You don't need to go too crazy but minimalize the surface agitation. Then you may have to crank up the co2 a bit to get the desired level but that should not be a big deal. Generally in a planted tank the wet/dry portion is unnecessary and you can just have your overflow go straight into a submerged sponge section to minimalize splash and noise.
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post #4 of 7 (permalink) Old 10-16-2015, 04:14 PM
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Surface agitation lets a lot of CO2 escape. If you're using pressurized CO2, it's not that big a problem. You can just increase the bubble rate as needed.

Wet/dry filters can also let CO2 escape. Covering the sump should reduce it, if it's a problem.
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post #5 of 7 (permalink) Old 10-16-2015, 04:54 PM
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I find surface agitation an insurance.

In non-CO2 enriched tanks it works to keep the CO2 nearer the equilibrium than a tank without surface agitation.

In CO2 enriched tanks it forms a top layer of water where the CO2 level is lower than the bottom layer which is richer in CO2 (as remarked the CO2 level can always be increased by increasing the supply).

This layer of lower CO2 water is a safer zone for the fishes.

As the level of CO2 rises in the bottom layers the fish find it more and more difficult to get rid of CO2 from their blood through their gills. This causes the CO2 level in the fishes blood to rise. This causes formation of H2CO3 to form in the fish's blood and ph of the fish's blood falls and causes the hemoglobin to lose it's ability to carry oxygen - this symptom is called hypercapnia.

Although the water is rich in oxygen, the fish cannot breath, and the fish swims toward the surface. If there is a layer of water which is lower in CO2; the fish finds relief in reducing the CO2 content in its blood - and this enables the fish to come out from the state of hypercapnia and oxygen becomes available to the fish.

So let the surface agitation to continue.

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post #6 of 7 (permalink) Old 10-16-2015, 07:22 PM
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Originally Posted by Jirajustin View Post
And, does a wet/dry filter impact Co2 levels in the water negatively?
The reason a wet-dry filter affects the co2 levels is that it increases the water contact with with the air. This allows for the co2 to escape the water easier. The "negative" impact is that you must increase your co2 output from your co2 tank in order to make the co2 saturation in your tank reach the desired levels

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post #7 of 7 (permalink) Old 10-17-2015, 07:05 AM
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This is one of those times that the lfs is correct. As others have stated, the bps will have to increase to compensate. For a plant only tank, this is no concern. CO2 is fairly cheap so blast it if you can. I aim for my drop checker to be a yellow green for my plant only tanks whether they have a sump or not. The way I have my sump setup, I have 0 surface agitation so I doubt if I loose much co2 at all. I also do not cover my sump since there is no water movement. High co2 concentrations pretty much assures me that my plants have plenty of co2 available during the photo period. I can't even tell you what my bubble rate is though. If I had to guess, it would be 20-25+. I use mineral oil too but the bubbles are so fast that it almost looks like a solid stream of bubbles.

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co2, surface agitation, wet dry filter

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