I received the following email from Jeff, a newsletter subscriber who has a very interesting point to make.
"I have been reading your emails when I can and enjoy the knowledge you share. I do have a question on this topic though.
Our local shop swears these aren't needed and manages 15 ponds without a filtration system. I decided not to buy one and for 4 months haven't had an issue. His theory is that with moving water, the proper number of plants, and fish, biological filtration can be a natural process.
He explained that there aren't filters in ponds and lakes and that there hasn't been for centuries, so why change what works. With proper setup and controls the pond should take care of itself.
If it wasn't working I would agree I need a filter but I am not sold. Have you any additional thoughts on that topic?"
"Hi Jeff,
Thanks for your email. This is my take on things!
First of all you do not mention how big the 15 ponds are. If they are very large and have a relatively low fish loading then it is perfectly feasible that the fish and other pond inhabitants are doing just fine simply because of the large volume of water.
A large lake for example will take care of itself naturally. Due to the volume of water and small number of fish the levels of ammonia will remain low.
In addition the large surface area makes it easy for atmospheric oxygen to dissolve into the lake with very little effort, especially if there is wind present which helps to break the water service and allow oxygen in.
The oxygen is critically important to the fish life and the nitrifying bacteria responsible for the breaking down of ammonia and nitrite into nitrate.
This is not always the case in smaller garden ponds where there is a smaller volume of water, larger fish load and subsequently higher levels of ammonia. The problem with these smaller ponds is how to remove ammonia.
Where your friend mentions "with moving water, the proper number of plants and fish, biological filtration can be a natural process" I would first of all like to talk about the moving water.
He mentions moving water because this helps to add oxygen to the pond because it makes it easier for atmospheric oxygen to dissolve into the pond. This is why many pond owners incorporate a waterfall or fountain system into their pond.
Where your friend mentions "the proper number of plants" I believe he is talking about using aquatic plant life to form a natural filter known as a Veggie Filter; sometimes known as a bog filter or plant filter.
A veggie filter (bog filter) consists of various species of plants which naturally use up the nitrogen based compounds excreted into the pond by your fish. This system can be effective but somewhat messy.
There are advantages to using a veggie filter such as zero electricity costs, a natural system working in the way nature intended as well as green water and blanket weed control.
The major disadvantage of using a bog filter however is when it comes to cleaning the pond. All plant life needs to be removed and the pond needs to be thoroughly cleaned at least once a year, usually in the fall (autumn).
The Question is one of How To Filter Ammonia Out?
The problem with not using a biological filter in a small to medium sized pond with a large fish load is the sudden increase in ammonia levels, particularly during hot weather.
In hot weather the high levels of ammonia combined with the ponds inability to hold as much oxygen as would be the case in cooler weather will lead to eventual poisoning of your pond fish.
As well as this the higher levels of ammonia (containing nitrogen) act as a food source for algae and blanket weed. These forms of plant life at night time use up oxygen in the pond water.
Whilst what your retailer friend states is true to some extent it is not always the case and in my opinion prevention is better than cure; particularly if you intend to keep expensive Koi or a high fish load in a small to medium sized pond.
I would advise you to take a look at the biological pond filter articles on my website. You may find them of some use.
Read the full article here ...
http://www.garden-pond-filters.com/Newsletters/Do_I_Need_A_Biofilter.htm
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