Owning an aquarium can bring a lot of pleasure and it is amazing to see fish and plant life living in harmony together. While many aquarium owners will spend time and money sourcing the most suitable fish and plants, one topic that is often overlooked is the level of oxygen in the aquarium. It is essential to get this right in order to sustain life as without oxygen fish, plants and other living organisms will die.
How does oxygen get into the water?
A gas exchange must take place in order for oxygen to enter the water and there are two main ways in which this is achieved – through plant photosynthesis (the process that takes place when plants convert light into energy, a process that creates oxygen as a waste product) or via surface agitation which can be achieved by a water filter.
It is possible to have both of these processes taking place in your aquarium at the same time which will boost the oxygen levels. However, oxygen also needs to be saturated (dissolved) in the water in order for fish and plant life to make use of it. The rate at which oxygen is saturated is dependent on the temperature of the water and the salinity of it, and the higher they both are, the lower saturation will be.
In order to understand this more take a look at the following table which shows a high saturation level of 100%, the average in a tank is around 70%:
Ppt is the measure of the salinity of the water while mg/l (ppm) shows the content of the dissolved oxygen in the water. For instance, an aquarium with saltwater that has a temp of 82.4F and a salinity level of 15ppt is able to dissolve 7.18 of oxygen.
You should be aware that the oxygen levels in an aquarium will change throughout the day – but not enough to make a huge difference to the health of your fish and plants. During the day the levels will be higher as more photosynthesis will be taking place for example.
It is vital to measure the oxygen in your aquarium and the dissolved content should be enough from 5-7 ppm. If this goes down to 4 ppm fish will be showing signs of being in distress, death is likely to occur if it reaches 2ppm.
While most aquariums have enough oxygen to sustain life it is important to monitor the temperature and salinity levels. If you notice any changes you will need to take action.
What can cause low oxygen levels?
- An aquarium that is overstocked can cause problems.
- No water agitation or too much.
- Lighting periods that are too short for the plants to produce enough oxygen.
- The filter is filled with waste.
- Rotting waste in the gravel of the aquarium. Anything that is rotting in an aquarium will use oxygen as the rotting process requires it, with this in mind you should always remove any dead plant life or fish that you notice immediately.
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