Real-time Monitoring of Dissolved Oxygen in Many Aquariums is a Great Safety Net Many marine aquarists only give the oxygen content in their aquarium water a passing thought, not fully understanding how the level of the Dissolved Oxygen (DO) in their tanks can affect their entire tank population. In one way or another, everything (fish, invertebrates, corals, algaes, bacteria) in the oceans and in marine aquariums react with oxygen. Most of the living beings of this planet require oxygen in order to metabolize nutrients. Fish, invertebrates, corals, and bacteria ingest O2 and expel CO2 day and night. Your critters are not the only things that use oxygen in your tank. Organic materials (i.e. Dissolved Organic Compounds, uneaten food and fish detritus on the bottom of the tank) consume a lot of oxygen as they break down. And now it’s even popular to add nitrifying bacteria additives which multiply very rapidly, consuming a large portion of the available oxygen in the tank water. Of all the organisms in your aquarium, large fish are the most acutely at risk to low O2 levels. In some situations with heavily loaded systems, simply the failing of a skimmer can bring the O2 levels down to dangerous levels and cause a chain-reaction fish die-off . This is where the PM3 Dissolved Oxygen module comes to the rescue. Get an Alarm and Also Have the Apex Take Action Should your aquarium O2 start to approach the danger zone, the Apex can alert you immediately by audible alarm as well as send you an email. But, that’s not all. You can have a couple of air pumps with air-stones on the ready in your sump and the Apex will turn them on if the O2 starts dropping too low. Now this is what aquarium monitoring and control is all about! Yet another example of how the Apex is like an Insurance policy for your tank. Bonus And, there is an added bonus, you get an extra temperature port as well as six I/O switch inputs. Purchase our optional I/O Breakout Box and you can monitor the off/on state of six I/O signals. This is useful if you want to set up an ATO (Auto Top Off), a feed button, or even a sump door alarm or light switch.