I believe some people use them for "show" because it looks nice. Another reason is to induce oxygen into the tank. There are some people that inject CO2 into the tank to promote plant growth. At night, plants stop taking in CO2 and take in O2 instead. With the CO2 running and nothing to take it in, the fish will gasp and die. The air stone adds O2 during the night. I personally just turn off my CO2.
for one, some people find that they look good. gives more movement in the tank. it also keeps the water circulated and promotes more oxygenation in the water (although some people say that it doesn't promote any oxygenation in the water)
but mainly, people use them for asthetic purposes...
Oxygen consumption, or addition , in your home aquarium is a constant topic of discussion among us fish keepers, but do we really understand what is going on inside of our tanks ?
If you are a little in doubt on this issue, you are like most home aquarium keepers. It can be very hard to imagine something that you can't see, especially when the ammounts are so small. Can you really imagine just how small 7 parts per million is?
Maybe the examples below, would be useful.
Say for example, you have a 135 gallon tank that you've stocked with 5 lbs. of various fish. The water in that tank is 79 degrees, with a pH of
7.0 , as per usual, you tend to feed a bit heavy (We love to see our fishies eat RIGHT !!) . Your fish are fed 1% of their body weight per day . Using well calculated formulas from the aquaculture society, this is how the math works out: Your 5 lbs. of fish will require .9 grams of oxygen per hour. That is equal to 21.6 grams of oxygen per day.These fish will produce .8 grams of NH3-N per day. The amount of oxygen needed by the bio-filter to convert this ammount of Ammonia to Nitrate and make of the bacteria happy, is 5.4 grams of oxygen per day.
This makes the total biological oxygen demand for your tank 27 grams of oxygen per day.
Now, what is a simple source for this oxygen. Air stones are by far the least expensive, and the most efficient way to aerate and add oxygen to the aquarium. Aeration can take place in the tank, filter, sump, or protein skimmer if youre a saltwater tank keeper. It makes no difference where the oxygen is added into the system, as long as it is present in adequate ammounts.
A pretty small, high quality air stone, will add a little less than .10 cubic feet of air per minute. Three of these stones will add 1.8 grams of oxygen to the water per hour, 43.2 grams of oxygen per day.
Oxygen saturation happens somewhere between 6 and 8 parts per million , this number depends on the temperature, salinity and elevation where you live. That means that the water molecules have absorbed as much oxygen as they can hold under those conditions. Any oxygen taken in beyond this point will be released back into the atmosphere with very little disturbance of the water.
75% oxygen saturation is not un-common in a well aerated aquarium, while 95% is almost impossible to achieve.
Since your tank has an oxygen demand of 27 grams, and the air stones are adding an oxygen level of 43.2 grams, there is no danger of a low oxygen stress condition.
Your tank will use and store only a certain amount of the available oxygen. And while its true that you can have a large amount of surface area in your biofilter, it is very unlikely that the bacteria will use all of it.
Remember, that the nitrifying bacteria are present in levels that are in direct proportion to the bioload of the tank. It doesnt matter to the bacteria how big your filter is. If they need and use only 10% of the surface area, that is what they will use. About 80% of the tank’s oxygen demand goes to the fish, with the other 20% going to the bacteria for the nitrification of organic waste.
So, your average fish tank is not using nearly as much oxygen to process the biological waste as you may have thought. While this has been long known by professional aquarists, it has taken a long time for that information to get to the aquarium hobbyist. Both wet/dry and fluidized bed biological filters utilize the same amount of oxygen to process fish waste. Sooooo...... are air stones useful beyond the pretty bubbles they produce????? I vote Yes
I keep one running in my co2 injected tanks at all times, they aid the plants and fish at night as well as keep O2 in the water. Yes they do bring in O2 just at the regular rate of 20% which our own air is made up of(all an air pump does is transfer the air in your house to the tank, nothing more nothing less) Co2 is 1% of the air we breathe so in turn it is bringing in O2 and Co2 however its at the 20% and 1% ratios.
Aesthetics are for people who dont know what to spend their money on.
scroll down about 2/3rds the way down the page, its a commercial air pump but it runs quieter then my coralife luft pump does. I like it because its variable and I can run plenty of tanks off one pump.
Thanks for all the advice. I have bought a pump and airstone. It works really well. My hopefully last question is about check valves. I understand you dont need one as long as the pump is higher than the tank? Is this correct?I actually bought one (a top fin one) which is terrible and doesnt allow much air through. So I am wondering if I should just return it or return it and get another type?
I've just installed one in my 70 litre tank to try and improve the circulation of the water and the O2 levels...it's certainly effective, but I don't know whether the flow is a bit intense for my fish and I can't see any way of adjusting it. Do people usually leave them on all day and night?
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