# What Fish Require Aeration?



## Venemous Rock (Jan 16, 2012)

What fish will require an air pump? My first aquarium is a four gallon I got for Christmas and it came with a filter. Do all fish need an air pump?


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## bmlbytes (Aug 1, 2009)

Air pumps are beneficial to most fish, because that is how oxygen gets dissolved in the water. Without oxygen, the fish would suffocate. Most hang-on-back filters offer enough water movement to dissolve oxygen in the water, but air pumps help too.


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## Obsidian (May 20, 2007)

You don't need an air filter to get the oxygen exchange. The oxygen exchange primarily happens at the surface of the water. Most filters have plenty of flow to meet that need. All it has to do is push the water in order for the surface to break enough to complete the exchange. The air pumps only create more agitation at the surface that increases the O2 exchange. The bubbles actually have little to do with it, they are too big.

So in short: You do not need an air pump/stone in any tank. I ran a 100ga just fine without one and that's a big tank


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## Venemous Rock (Jan 16, 2012)

I have one of those internal type submergeable filter with the black, rough spongy stuff. I believe its referred to as a charcoal filter or something.


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## bmlbytes (Aug 1, 2009)

If it is completely submerged (like some filters for small tanks are), I would recommend either moving it to the top, so it splashes a little, or using a small air pump. Its all about the surface movement. If there is no movement at the surface, an air pump would help.


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## Venemous Rock (Jan 16, 2012)

bmlbytes said:


> If it is completely submerged (like some filters for small tanks are), I would recommend either moving it to the top, so it splashes a little, or using a small air pump. Its all about the surface movement. If there is no movement at the surface, an air pump would help.


Yes, the filter is completely submerged except for the cord which runs it to an electricity outlet. I'm going to assume you mean have it partially out, like where the water would shoot out of it was above the water level. If so, I will pull it up a bit so the water splashes out.


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## bmlbytes (Aug 1, 2009)

Yeah exactly. Do that and you should be good.


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## Fishpunk (Apr 18, 2011)

If you house a betta in there, you don't need an air pump at all, though you will need a small heater.


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## Betta man (Mar 25, 2011)

bettas don't need oxygenation, but stagnant water isn't great. A gently current is best. For other fish, unless you have a lot of fish in a small aquarium, a filter should provide sufficient oxygen.


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## Venemous Rock (Jan 16, 2012)

bmlbytes said:


> Yeah exactly. Do that and you should be good.


How much should it be out, completely, or the tiniest bit? Just enough so all the water flows out?


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## Betta man (Mar 25, 2011)

see what your fish do best with.


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## Fishpunk (Apr 18, 2011)

Stagnant water can be dealt with via water changes of by putting a small filter in the tank, either mechanical or sponge. With sponge, you get surface agitation whether you need it or not.


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## bmlbytes (Aug 1, 2009)

Venemous Rock said:


> How much should it be out, completely, or the tiniest bit? Just enough so all the water flows out?


Just enough to make the surface of the water move.


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## Betta man (Mar 25, 2011)

water changes won't do much unless it's every few 3 days. A air pump or filter is way easier and a filter will make it so you don't need as regular water changes.


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## Mikaila31 (Nov 29, 2009)

No fish needs an airpump. With the tanks I run I aim for as little surface movement as I can and this has never caused a problem. All my tanks have basically zero surface movement. I also have 2 stagnant tanks with practically no water movement. One is my fry tank and supports fish just fine with just a heater and heat pad, no filter or airpump. 

As mentioned airpumps don't actually add oxygen to the water. They simply aid in diffusion by moving water from the bottom of the tank to the surface.


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## Betta man (Mar 25, 2011)

I disagree. It will slightly increase the oxygen in the water.


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## Fishpunk (Apr 18, 2011)

Mikaila31 said:


> As mentioned airpumps don't actually add oxygen to the water. They simply aid in diffusion by moving water from the bottom of the tank to the surface.


Not correct. The surface agitation caused by the bubbles increases the dissolved oxygen content.


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## Venemous Rock (Jan 16, 2012)

Okay thanks everyone. I settled for two goldfish since my tank is only four gallons.


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## Fishpunk (Apr 18, 2011)

Oh boy. Here we go again.

That was a poor choice. Goldfish need a large tank, so you are going to need a 55 gallon tank in a few months or the fish will experience stunted growth. And since goldfish are messy, you will be constantly cleaning that tank.

Others will elaborate, I'm sure.


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## Obsidian (May 20, 2007)

Fancy goldfish:










Common Goldfish: And these are small, they can get up to a foot and half long









All way too big for a 4 gallon tank. Sorry


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## Mikaila31 (Nov 29, 2009)

Fishpunk said:


> Not correct. The surface agitation caused by the bubbles increases the dissolved oxygen content.


Yes while surface agitation can increase oxygen diffusion, you still need water that is not O2 saturated. Oxygen is added to the water by diffusion, nothing else (except plants). If water is saturated in oxygen diffusion of O2 from the air pretty much stops and all the agitation in the world will not increase the dO2 content. Agitation is not going to increase the dO2 content any more then good water circulation, since diffusion occurs only at the surface. Usually the most oxygen depleted water is the deepest. 

Only with very productive plants and minimal surface movement, or actual oxygen injection can you go past the saturation point.


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## Fishpunk (Apr 18, 2011)

Um..If the water is oxygen-saturated, why would you try to add more oxygen? This is a problem aquarists don't have.


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## Mikaila31 (Nov 29, 2009)

Fishpunk said:


> Um..If the water is oxygen-saturated, why would you try to add more oxygen? This is a problem aquarists don't have.


Do you monitor dO2? A container of water with no oxygen at all left just sitting will relatively quickly obtain oxygen equilibrium with the air just through diffusion. Fish and our bacteria consume very little oxygen. 

Its not hard to achieve oxygen saturation. I keep planted tanks both high tech and low tech. I don't use air stones and avoid surface movement all my filters are either internal or canisters that cause little to none aggitation. Then some tanks get CO2 injection while some don't. Regardless you get situations where plants pearl. That is were you can actually see the oxygen produced by the plant forming bubbles. This may occur for two major reasons, oxygen production is higher then rate of diffusion or the water becomes saturated with O2 and resists going above equilibrium(some what). This is one of natures ways of adding oxygen to water, so much so that algae produces most the oxygen in the atmosphere.

If it helps I have a 20 high with WAYY more fish then I should. No aeration at all and just a slight current off the surface. I have a habit of unplugging the filter at night since its only needed some of the time. If I forget to plug it back in the tank takes a good 14 hours of no movement before o2 levels become an issue. Thats in a seriously heavy stocked tank with plants.


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