The crystal clear water in your garden pond is not down to you, it’s down to the micro-organisms and beneficial bacteria that live in your ponds filter system and in the pond water itself, but what is beneficial bacteria.
Beneficial bacteria is there to break down all the nasty stuff in you pond, like fish waste (poo) rotting leaves, uneaten fish food, dead plants, dead algae, in fact it breaks down any organic matter that exist in your pond, plus it stops your pond smelling bad.
If your pond didn’t have beneficial bacteria, pollutants would build up causing problems with water quality, sludge would build up on the bottom of your pond, algae would get out of control and your fish would get ill and possibly die.
Beneficial bacteria can also help to reduce nutrients like nitrogen and phosphorus which can also become a problem in your pond.
There are two types of bacteria you need to know about, you have aerobic bacteria that needs oxygen and anaerobic bacteria that doesn’t need oxygen, the funny thing is they often need each other to survive, multiply and keep your pond clear.
The aerobic bacteria digest organic matter really fast and turns harmful ammonia into nitrites and then into harmless nitrates which are then absorbed by pond plants, this is called the nitrogen cycle.
The anaerobic bacteria live in areas where there is no oxygen and will die where there is oxygen, it breaks down organic waste slowly which creates sludge at the bottom of your pond, the problem with this is you get a by-product of hydrogen sulphide which smells like rotten eggs.
As I’ve said the two types of bacteria often need each other to keep your pond clean, the aerobic bacteria does most of the work but at a cost, they digest and break down all the organic matter, as they do this they reproduce and as they reproduce they digest more and use more oxygen, eventually the oxygen will be depleted, they will run out of food and die back.
This is where the anaerobic bacteria step in, it’s usually hiding at the bottom of your pond, when the aerobic bacteria use up the oxygen the anaerobic bacteria that doesn’t need oxygen gets to work finishing of the waste, it’s a lot slower at digesting and breaking down the organic waste, but as they digest the waste they realise nutrients into the pond, this feeds your plants, the plants will produce more oxygen and when the oxygen levels are restored the anaerobic bacteria dies off, the aerobic bacteria builds itself up again and takes over, it’s one big circle that both bacteria play there part to keep your pond nice and clean.
Having said all of that it’s much better to have a good colony of aerobic bacteria in your pond than anaerobic bacteria, aerobic bacteria thrives in oxygen rich environments so it’s a good idea to encourage its growth, having waterfalls fountains and air pumps are a great way to get oxygen into your pond and don’t let organic matter build up.
It takes up to six weeks for beneficial bacteria to colonize your pond and filter, so adding beneficial bacteria to a new pond is a great idea, you can also add it to a mature pond to give it a boost especially during the spring months when your pond is starting to come alive after winter, and by the way you can’t overdose with beneficial bacteria.