Tag Archives: sludge

Preparing Your Pond For Winter

For any enthusiastic gardener, autumn is a perplexing time. Your arduous work throughout spring and summer begins to fade away, with the promise of next season and another fruitful crop just on the horizon. Pond keepers are no different in this respect; they toil all year to fight off algae blooms and keep their pond in the best condition for its inhabitants, only to be bombarded with algae come spring. The thought of having to cover up the pond, no longer being able to sit around and enjoy it with a cold drink in hand, can be a little sad. However, with a little maintenance during autumn and winter, your pond will be match fit for the first sign of a warm spring day.

The main priority for any pond owner throughout the year is to keep the pond water ‘healthy’. If the water parameters are correct in terms of pH and KH (carbonate hardness), you will provide a healthy environment for aquatic wildlife, fish and beneficial bacteria. It cannot be stressed enough, that without the water parameters being correct, beneficial probiotic bacteria will struggle to deal with the unwanted organics added during autumn & winter that elevate the risk of fish & wildlife death and algae blooms in spring.

Without any care or maintenance over autumn and winter, ponds begin to form a layer of sludge on the bottom from unwanted organics such as leaves, twigs and faecal waste from fish and wildlife. Whilst frogs and newts love to lay in this sludge, if left untreated, it can cause an imbalance in the water, making it poisonous to wildlife and fish by discharging Hydrogen Sulphide (H2S) gas from anaerobic bacteria inside the sludge.

Essential Autumn Care Tasks
To prevent an algae bloom in spring, complete these simple tasks during autumn:

Check your water quality

After a spring and summer of algae, acidic rain and fish waste your pH and KH levels will need adjusting. The pH should be between 7 & 8.3 and the KH level should be above 5. You can either buy a quality testing kit, take a sample of water to your local water garden centre or simply use Pond Equaliser to instantly stabilise the pH at 8, and KH above 5. Pond Equaliser will also remove any ammonia and heavy metals to create a safe and healthy environment for fish, wildlife and beneficial probiotic bacteria.

Add bacteria

Add quality, probiotic bacteria that are capable of working at temperatures lower than 08°C. Use Pond Klear for smaller ponds, Natural Pond Klear for larger natural ponds and Winter Pond Treatment for the colder winter months. Task-specific probiotic bacteria slowly digest any debris and unwanted organics and reduce the toxic H2S levels.

Tend to plants

Prune back any aquatic plants and remove any floating debris from the pond; this debris can be deposited in a compost heap as it is high in nitrogen and other essential nutrients for plant growth. Don’t forget to check for any wildlife that may be hibernating when removing aquatic plants or sludge; newts and frogs will hibernate in sludge and dragonfly larvae can lie dormant in plants for several months. When you remove any debris or plants from a pond, leave them at the side for a couple of hours to allow any wildlife to make its way back to the pond.

Cover up

Cover your pond with a net to catch leaves and twigs; leave gaps around the edge to allow wildlife to get in and out of the pond. The frogs and newts that may be hibernating at the bottom of the pond will be ready and waiting to eradicate slugs and snails in spring.

Put your fish on a diet

Feed fish less as the temperature drops, or consider moving to a low protein food. As temperatures drop, fish eat less, once it gets below a certain temperature they will stop feeding. If you continue feeding them, the wasted food will break down, release nutrients into the water to feed any algae and will add to the layer of sludge at the bottom.

Deep clean

If you have a filter, clean it thoroughly in autumn to remove any algae or debris trapped during summer and clean monthly throughout autumn and winter.

Keep it moving, slowly

Keep pumps and filters running all year; they will continue removing debris and prevent the pond from freezing over. If possible, turn the flow rate down to avoid cooling the water further. If water freezes over, it restricts the available oxygen for fish, and seals in the toxic gases that can be released from decaying organics.

Check your water quality, again…

Most important of all, get the water parameters right to increase the ponds biological self-cleaning ability, as this will reduce the amount of work required, and increase the enjoyment of your pond in spring & summer 2018.

For more information on why ponds go green in spring, read our blog post here.

The pond sludge problem

Every garden pond has sludge. It’s part of the natural balance of pond life to form a layer of dark, thick gunk on the pond floor and most of the time it’s nothing to worry about; but when ignored it can prove fatal to plants, fish and other wildlife or, at the very least, make your garden smell like rotten eggs.

Even with the best will in the world and a lot of spare time, you can’t stop things falling in your pond. Leaves from overhanging trees, bird droppings, and plant cuttings are all going to end up in there. All this, added to the matter already in your pond, sinks to the bottom and forms the layer of sludge. The sludge is a mixture of organic and inorganic matter which is mostly biodegradable in the right environment.

Now, a small layer of sludge isn’t anything to phone home about, but when it starts to build up and is left untreated it starts to starve the pond of oxygen. This lack of oxygen causes increased activity in anaerobic bacteria (the bad kind), which in turn produces hydrogen sulfide. Hydrogen sulfide is best known for producing a foul, rotting egg smell but it can also be toxic to fish and plants in large doses.

Not only can it kill plants and wildlife, it can also kill off the aerobic bacteria which eats the pond sludge. Unfortunately, this creates a vicious cycle where the pond sludge increases, the hydrogen sulfide increases with it, and the pond becomes more toxic. Here’s the process simplified –

Sludge infographic attempt

How to fix it

It might seem like an obvious suggestion but the first step is prevention. Do everything you can to avoid organic matter falling into your pond –

  • Keep bushes, trees and plants trimmed so there isn’t much overhanging
  • Clean your pond regularly with a net to get out any floating debris.
  • Use a bird deterrent (scarecrow etc) so they aren’t as prevalent.
  • Keep a net over the pond to stop any larger debris getting in.

The second step is to physically clean out as much sludge as you can. Arguably the easiest way to do this, in a small pond, is by shoving a (gloved) hand in and pulling it out, but you can also use a net or pond vacuum. Admittedly, I’ve never used a pond vacuum but I have heard mixed reviews. Some people complain that it can suck up any smaller pond life (tadpoles etc) but you’ll have to use your own better judgement on that one.

The final step is to add to the aerobic bacteria in the pond. There are a few products out on the market including our own Envii Sludge Klear! By adding to the aerobic bacteria, you are increasing the rate at which the sludge is being eaten. Not only will this help with sludge but it will also improve the environment for fish and plants. It also contains facultative bacteria which break up the sludge, allowing the filter to consume it easier. Sludge Klear also works as low as 4°C which means you can use it through the winter and avoid the inevitable build up in early spring.

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