Air stones: Let's get scientific.

[josh909]

So, I've read that you can run them 12 hours a day (IE: when my aquarium lights are on), and that is sufficient...

I'd like to get more factual and scientific about it.

When it comes to air stones:

For X tank size and X number of fish (assuming no live plants... for now)
## I don't have a DO meter, but I'm sure some of you fine fish folk do!
## I'd like to create a little algorithm and web app for this, once I have some reliable numbers.

• What size stones?
• What size air pump? (Single, Double, Quad Line? What wattage or GPA? I heard GPA is a somewhat inaccurate measurement of an air stone)
• How many stones? (does this affect nominal running time if I have multiple? I assume, yes. What about fine bubble/nano stones that claim higher dissolved oxygen?)
• Running time to reach nominal oxygenation?

Any help would be much appreciated!

Disclaimer: Not sure if an application and/or method already exists for air stone requirements/measurements, I'm new to this fish thing.

 

[Deleted member 149562]

I have an air curtain which is attached to a 400 lph air pump

It is running 24/7 along the back of a 200 litre aquarium

In the past I have had normal airstones and air curtains and have always run them 24/7. (I also use filters that enable aeration too)

Unlike a natural setting like a river, an aquarium has no real movement per se. The movement of the water provides oxygenation compared to static water that doesn't provide anything at all and you get fish on the surface with snouts above the surface often gasping.

Filters do move the surface of the water to a degree but then you need to be careful as some fish cannot tolerate high rates of filter flow. A river flow has various flow rates, whereas the filter is static flow rate.

So an airstone or air curtain can be very beneficial, especially for the fish who occupy the lower levels of an aquarium where the flow/aeration from the filtration might not be so good and even moreso if the aquarium is deeper than usual such as a "high" 20g instead of the usual 20g long.

There can never be too much aeration/oxygenation imho so leaving the air curtain or stone running 24/7 is beneficial to the fish in my own experiences.

 

[itiwhetu]

I run an air curtain at the back of my 150 gallon and always will run some sort of air on a tank.

This is how I see it; the air curtain moves water from the base of the tank to the surface, more importantly it aids gas exchange from the tank to the atmosphere. If an air curtain is functionally properly it can double the surface area of your tank therefore double its capacity. If you do not have an air curtain the surface of your tank will be flat, if you add an air curtain it will ripple the surface, and the surface looks like a piece of corrugated iron, increasing the surface area of the tank, and its capacity.

 

[CaptainBarnicles]

I need me a new air curtain, got a link for one you'd recommend please?

 

[Deleted member 149562]

I need me a new air curtain, got a link for one you'd recommend please?

This is the one I am using and where I got it from....

Interpet Bubble Wand Flexible Airline

Interpet Air Diffuser is ideal for aquariums needing a bubble curtain. Also ideal to replace the Interpet LED Bubble Wand air diffuser.

www.aquacadabra.com

I use the 34cm one that is £3.96

 

[Naughts]

I don't use air stones. The filters facilitate gas exchange.

 

[Boundava]

Agree, filter will also increase surface agitation, especially HOB and canisters with spray bars lever to/angle at the surface. I have had air stones but they clogged after a period of time. The smaller air pumps also have varying levels of humming/vibration that can become annoying depending on the model and its movement (walks off the shelf, or one side isn't level with the other). If I see a tank needs more current/movement I will add a current maker or powerhead and have it at the surface or angled at it. Now many have venturi attachments to add air to the exiting water, increasing gasses in the water

 

[josh909]

I don't use air stones. The filters facilitate gas exchange.

What type of filter provides the best gas exchange, do all of the different types do this?

 

[Deleted member 149562]

I have two means of filtration....recently changed from a 24w GKM to an Aquael Uvifilter 750 and I have the main filter, an Aquael Turbo 2000, both internals.

This is the Turbo doing its aeration. Both filters are doing aeration along with the air curtain at the back. The filters move the surface quite a bit but I like to have aeration from the substrate levels too for the lower quadrant fish

 

[Lajos_Detari]

What type of filter provides the best gas exchange, do all of the different types do this?

Some internal filters as shown by @wasmewasntit above come with venturi where they suck air from the outside of the tank, and push the air into the water.
This works the same as an air stone though it pushes the gas from the middle level of the tank or depending on where you place the internal filter.
If you place the internal filter at the bottom of the tank, then the venturi will push the air from the bottom of the tank.

If you used an air stone, it will push the air/gases from the bottom level of the tank to the surface which is even better than a venturi from an internal filter.

Some people use a water pump with venturi which work similarly to an internal filter.

Other types of filters won't be able to push as much air as an internal filter with venturi or air stone into the water.

Take note that having gas exchanges or enough oxygen in the tank is the most important thing unless you only have a few small fish in your tank.
It's the same as human where oxygen is the most important for us, more important than food and cleanliness, etc.

If you are having big fish, it's good to have a big airstone and venturi.

 

[itiwhetu]

Some internal filters as shown by @wasmewasntit above come with venturi where they suck air from the outside of the tank, and push the air into the water.
This works the same as an air stone.
Some people use a water pump with venturi which work similarly to an internal filter.

Other types of filters won't be able to push as much air as an internal filter with venturi or air stone into the water.

Take note that having gas exchanges or enough oxygen in the tank is the most important thing unless you only have a few small fish in your tank.
It's the same as human where oxygen is the most important for us, more important than food and cleanliness, etc.

If you are having big fish, it's good to have a big airstone and venturi.

The venturi system doesn't work like an airstone, an air stone moves water from the bottom of the tank, a venturi from the surface.

 

[Naughts]

What type of filter provides the best gas exchange, do all of the different types do this?

My understanding is that as long as the surface is disturbed, thus breaking the surface tension, gas exchange is taking place. This is sufficient to introduce oxygen and expel carbon dioxide. So any filters which are driven with enough force to disturb the surface. My small tanks have pump operated sponge filters (Chinese manufacturer), my medium tanks have internal filters where the nozzle can be directed to the surface (Juwel). I've never had concerns that the fish don't have enough gas exchange.

Obviously set ups can be very different, mine are low tech planted, no CO2. I don't have very large tanks that require more than one filter or powerheads. I don't have fish requiring a fast flow but that is a different aspect to consider too. And finally, higher levels of oxygenation are required if there is illness, chemicals like medication, or high temperatures in the tank - these scenarios are rare for my tanks.

 

[Uberhoust]

This is an interesting subject and I am looking forward to hearing other points of view. Here are some of the thoughts I have on the subject.

1. Gas exchange is nearly or entirely from the Air/Water interface the effectiveness is based on following:
   1. The surface area of all the Air/Water surfaces (this is not affected by the hydrogen bonding that creates surface tension, though it can be influenced by oils or protein scums)
   2. The temperature of the water, warmer water cannot hold as much dissolved oxygen
   3. The current amount of dissolved oxygen in the water, if it is already saturated, aeration will not improve it.
2. Gas exchange through the water column is significantly slower than the exchange via the water air interface. The dispersal of oxygen through the water is primarily achieved by mixing which is were the HOBs or other current inducing filtration can be helpful as they create a mixing current exposing potentially oxygen depleted water to the air water interface.
3. As bubbles decrease in size they provide a larger surface area per volume of air. This is why carbon dioxide diffusers often use ceramics with very small pore sizes. Unfortunately making small bubbles also increases the back pressure on the air lines and can reduce the life of an airpump.

Personally I do not use air in my tanks normally but I keep pumps and airstones available so that if I encounter an issue I can add them quickly. I found the MarineLand air stones that are made of a piece of felt sandwiched between two plastic halves easy to maintain with reasonable bubble sizes.

It should be noted that it isn't just Oxygen we need to worry about it is also the diffusion of other gases such as CO2, Nitrogen, and Ammonia. All can be absorbed into the water or diffused from the water. I once thought how bad can it be to clean the outside glass front of my tank with Windex. I was real bad, within 20 minutes all my fish were in distress, the initial treatment was to add aeration. Ammonia is hydroscopic but it is also a gas that can be diffused.

Overall surface area and mixing are the primary ways that help water to stay oxygenated. Aeration can help with both but is not necessary for a lot of aquarium configurations.