I normally don't use an aerator for my fish tanks, but I also don't usually have my fish tanks anywhere close to being full of fish.

I've set up a new aquarium recently, with the plan to have community/schooling fish in it, and so I would actually like to have it stocked as full as I'm comfortable with.

Keeping the water parameters stable is easy, but what I'm worried about is the levels of oxygen in the tank. The water isn't going to be moving like I have in my other tank, so I want to be able to measure the oxygen levels to make sure they don't get too low and if I will need to set up an aeration system.

Is there a way I can test the levels of oxygen in my aquarium?

1 Answer 1


You can buy a dissolved oxygen meter, but they'll generally start in the US$200 to US$400 range, and a suitable one I believe runs closer to US$500-600. Not exactly an everyday piece of equipment for a measurement you're going to take once. There are cheaper test kits designed for other applications, but those will only get you in the approximate ball park, so I'd say that's not really going to be much use in this application.

The typical way to know if your fish are getting enough oxygen is to observe if your fish are continually gulping at the surface of the water. Oxygenation occurs any time oxygen-poor water comes in contact with the air at the surface. But there's no magic to an air stone that is going to "put oxygen" in your tank. Aerators and such are just another way to circulate water and to create surface agitation. Any filtration system (or even a simple circulation pump) that takes in water from below and releases it towards the surface should provide sufficient agitation in your tank to meet your fish's oxygen needs… unless you are overloading it.

Honestly, if you're overloading the tanks enough to worry about oxygenation, I think you will run into a lot of other problems first. Usually the number/size of fish an aquarium can support is determined by the nitrogen cycle (the ability to get rid of waste), not oxygen absorption. But if your fish are gulping at the surface for oxygen, you'll either have to increase the water circulation, or reduce the number or size of your fish. But buying an expensive piece of equipment to know the exact mg/L oxygen saturation isn't a typical diagnostic for the home aquarist.

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