# Air Pumps for a 125gal



## CinBos (Feb 24, 2012)

I've never really had an air pump before with my aquariums. I figured its time to pull the plug on them, because they can be used for more usefull things rather than just aesthetics. I was curious though, do I need the highest rated air pump for my 125 gal or can I get away with an air pump that is sufficient enough for a 75gal aquarium? The tanks height is 21", and I plan on having 2 air stones in the aquarium.


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## Fishy_Cichlid (Aug 4, 2011)

Very debateable subject  You will find a lot of posts here in C-F with pros & cons on either side. Fact is, fish need oxygen. And Air-pumps are just not the ONLY way you can oxygenate your tank. Infact, you could for Ex. use a powerhead or you could even use a spray-bar with your filter/canister returns. Anything which breaks the water surface will do the job. Again, needs mentioning, that air enters, between the water molecules, when its surface tension is broken. For Ex. with a spray-bar. Again, nothing wrong, if you do want to use a air-pump in combination with airstones.

Longer the airstones (and more holes in them), the more bubbles they form. Again, smaller the holes, smaller the bubbles, so more air/oxygen is able to get into the water molecular spaces. With a 125 G and 2 airstones, a air-pump around 15 L/Min would do the job. IMO, if I were to put airstones/airpump combo, I would just not depend on that alone and would also put in a powerhead. Quite often, you will find the airline coming out of the airpump inlet. And if it was night time and you didnt happen to notice the loose pipeline, its better to have a backup in the form of a powerhead or a spraybar.


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## CinBos (Feb 24, 2012)

Fishy_Cichlid said:


> Very debateable subject  You will find a lot of posts here in C-F with pros & cons on either side. Fact is, fish need oxygen. And Air-pumps are just not the ONLY way you can oxygenate your tank. Infact, you could for Ex. use a powerhead or you could even use a spray-bar with your filter/canister returns. Anything which breaks the water surface will do the job. Again, needs mentioning, that air enters, between the water molecules, when its surface tension is broken. For Ex. with a spray-bar. Again, nothing wrong, if you do want to use a air-pump in combination with airstones.
> 
> Longer the airstones (and more holes in them), the more bubbles they form. Again, smaller the holes, smaller the bubbles, so more air/oxygen is able to get into the water molecular spaces. With a 125 G and 2 airstones, a air-pump around 15 L/Min would do the job. IMO, if I were to put airstones/airpump combo, I would just not depend on that alone and would also put in a powerhead. Quite often, you will find the airline coming out of the airpump inlet. And if it was night time and you didnt happen to notice the loose pipeline, its better to have a backup in the form of a powerhead or a spraybar.


I am familiar with the surface agitation. I have 2 filters, a canister and a HOB, that are creating enough surface agiatation to create more oxygen. The air stones would be more for visual affects, and I happen to find them very pleasing to look at. But thanks for the info on the air stone themselves, was also going to be another question.


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## BillD (May 17, 2005)

The size of air pump needed would depend on the depth of the tank. The ratings of tank size on air pumps are rather stupid. A 21" deep tank will need a certain pressure for the air to get to the bottom regardless of the gallonage of the tank; it wouldn't matter if it was a one gallon cylinder or a 10,000 gallon pond. A consideration seldom mentioned is that not all air stones are created equal. Some will offer resistance even when new.If you blow through an air stone it should feel effortless. Over time they will often clog, creating back pressure and reduced flow. Some can be cleaned with things like bleach, others will disintegrate. Some have replaceable foam diffusers, and these work very well until they clog,at which point you replace the foam. 
In my experience, even small cheap pumps like the Hagen Elite 800 series have no difficulty pumping down 18", and I think they would still work at 21". If you need a large volume of air (such as for multiple air lines), a bigger pump capable of more volume might be needed, as long as the minimum pressure were met. As well, the amount of air flow you want, as opposed to need, might dictate the pump size.


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## SupeDM (Jan 26, 2009)

i love the hagen elite and optima series air pumps when just trying for aesthetics. They are cost effective and their rebuild kits are cheap and easy. I have some that are insanely old and buy any used ones i find if they turn on at all. However now that I am starting to max the electrical capabilities of my home it has come to the point where I had to make a decision whether to invest in a central pump and sponge filters or cut out the air all together. And i went for the pump.


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