Fish Pond Water Quality Basic Introduction
You look into your perfectly clean and clear pond, you see fish darting around, they come to your hand to feed having lived happily in their home for well over 2 years. The plants are growing well and you are pleased with your investment and especially that you have never lost a fish.
This desirable situation is made all the more possible when you understand something about water quality and what is happening in a pond.
The fundamental and single most important factor behind good water quality is excellent biofiltration. Poor filtration will undoubtedly create poor water conditions that in turn will result in water looking poor, fish disease and even death.
There are specific parameters that indicate good or not so good water quality. Before talking about each of these in turn lets look what happens in ALL ponds containing fish and especially what happens just after feeding takes place.
1. The fish eat the food and secrete nitrogenous chemicals from their gills and bladder. The main chemical is ammonia - that's the chemical with a very pungent smell that is contained in some household cleaners. The more food eaten then the more the ammonia produced.
2. If all is well in the pond biofiltration process the ammonia is diluted and quickly converted in the biofilter to another nitrogenous (contains nitrogen) chemical group referred to as NitrITEs. As time proceeeds and all being well this happens very quickly the nitrites are converted to NitrATEs.
Remember the following: nitrITEs are very poisonous to fish and nitrATEs are about 500 times less poisonous to fish. Ammonia is the most poisonous of all three.
3. This sequential conversion process from ammonia via nitrites to nitrates takes place in a biofilter in the presence of two special bacteria AND oxygen and certain mineral requirements normally contained in the water in small quantities. The bacteria need oxygen to live and metabolise and to also drive the oxidation process that first of all converts Ammonia to NitrITE and then this to NitrATE.
No oxygen means no conversion and therefore poisonous conditions in your pond will prevail.
4. Now in the beginning and if you have few fish and lots of water and no biofilter the poisonous chemicals will be diluted and may not pose an immediate threat. However when you feed again the levels get higher and so it goes on until one day your fish start looking sick, becoming short of breath (come to surface and try to gulp air), swim haphazardly and maybe even die. If you change the water or portions of it frequently you can lower the levels of poisonous chemicals. The writing is however on the wall. Unless you prevent the build up of ammonia and or nitrITEs your fish will one day die.
5. How would you like to live in your own toilet?
6. When a new pond is built and the intention is to hold fish it is IMPERATIVE that a biological filter of adequate size and good design is installed. Even when you install the filter it will still take up to six (yes 6!!!!) weeks for the biofilter to start to function at high capacity. This is the time it takes for the level of bacteria to build up to sufficient numbers to do a good job of converting the poisonous chemicals to more friendly chemicals namely nitrATes.
The biological filtration process also cannot start unless there is a source of nitrogen for the bacteria to consume. So a small quantity of fish is required to start the process - in other words waste product from the fish is the food source for the bacteria.
These first fish in a new pond will take some strain inevitably so do NOT put too many fish in a new pond and certainly do NOT put that prize koi in the pond for some 6 weeks or so.
7. How do you know if the level of ammonia or nitrite is too high in a pond? There is only one way. You have to measure it using test kits. If you do not want to take this trouble (I do however recommend it) then in the first couple of months of installing a new pond with a biofilter do frequent water changes - say 50 litres per day in a typical smallish garden pond and do not overstock with fish. After the 6 weeks are up introduce more fish slowly and not all at once. Give the biofilter time to adjust to the higher levels of ammonia that will be produced following the introduction of more fish.
8. In the highest quality pond water there is no ammonia and there is no nitrite except for a very short period after feeding takes place.
This is your sole aim of biofiltration namely to get the poisonous chemicals secreted by fish down to virtually ZERO concentration levels. The fact that the biofilter also removes solids is a bonus.