Filtration what it does & NPS

[koinut]

Filtration, what it does, and NPS).

I think the best way to describe what a pond filter actually does is to describe it as the ponds sewage plant, it treats and removes all the harmful pollutants that builds up in our ponds.
It does this mechanically and biologically, and there are many different makes and types of filters available for us to purchase and use but at the end of the day they all have the same basic function to perform.
Filters have many different types of media inside them for performing the cleaning process and the removal of harmful pollutants.
This can be in the form of brushes, sponges, matting, plastic rings, lava type rock (Alfragog), beads, sand, and many more, the list is endless.

Lets take the mechanical side first.
This generally takes the form of different grade sponges or brushes etc.
These remove all the heavier debris and deposits we have present in our ponds like leaves, dust, pollen etc. All this debris is collected in the filter media for us to remove by hand.
This side of the filter process is fairly self explanatory and easier to understand than the far more important biological side that deals with the pollutants that build up in the pond.
Most of these pollutants come directly from the fish themselves and us via feeding them.

So lets move on to the biological side of the filtration process.

Within the filter we have what is called the filter bio-media this is where the filter bacteria colonize and multiply and deal with the pollution in the pond water. To understand better we need to know what goes on in the pond and what process’s take place.
Firstly we have our fish causing the majority of the pollution which comes directly from their respiration (via their gills) in the form of harmful ammonia.
We also have harmful ammonia coming from their excreta, and from anything rotting in the pond like uneaten food.
Luckily for us nature comes to our rescue (or rather the fishes rescue) and deals with all this pollution.
Over a period of time Nitrifying bacteria colonize our filter media, there are two different types of bacteria living in our filters, firstly we have what’s called Nitrosomona’s bacteria, these deal with the harmful ammonia present in our pond.
Unfortunately whilst the Nitrosomona’s process the harmful ammonia they produce as a by product harmful nitrite.
Nature to the rescue again.
The second type of bacteria (Nitrobacter) then convert this harmful nitrite in to far less harmful nitrate.
And this can be dealt with by our weekly partial 10 - 15% water changes.

Nitrifying bacteria and its performance are greatly effected by temperature and also food supply, you can also add to this their need for a constant supply of good quality well aerated water.
Nitrifying bacteria can in no way stand drying out, they will die.
If they lose their supply of well aerated water for more than 4 or 5 hours they will start to die back quickly.

The temperature for optimum growth of nitrifying bacteria is between 77-86° F (25-30° C).
Growth rate is decreased by 50% at 64° F (18° C).
Growth rate is decreased by 75% at 46-50° F (7.7C - 10C)
No activity will occur at 39° F (4° C).
Nitrifying bacteria will die at 32° F (0° C).
Nitrifying bacteria will die at 120° F (49° C).

From this you can see the great difference in the performance between the seasons.

Also one of the most critical times for pond keepers is when we are starting to stock a new pond, this is when we encounter what’s know as NPS (new pond syndrome).
Obviously when we turn our new filter on it is barren of any Nitrifying bacteria, it has to be colonized before it can deal with any pond pollutants.
If we were to add to many fish to quickly it just will not have the time for the bacteria to colonize quick enough to deal with the pollutant (ammonia).
This is when we suffer large spikes of ammonia in a new pond.
But if we add our fish gradually over a period of time the bacteria has time to colonize the filter media and deal with the gradual rise in pollutant levels.
It is normal to encounter first the rise in ammonia and then a rise in nitrite.
This is because the second type of bacteria (Nitrobacter) take longer to colonize the filter media, hence the rise in nitrite.
During these initial spikes you can deal with the problem again with partial water changes.
At these critical times its essential to keep a close eye on water parameters and adjust any problems accordingly with your partial water changes.

Andy T (koinut)