If your garden pond filter isn't working correctly or efficiently enough, you can end up with murky or almost muddy looking pond water. If you have koi or gold fish in your pond, the fish can become ill from the dirty water, and the pond can even have an unpleasant smell. The murky water can become deadly to fish quickly. The algae is less serious and can actually be beneficial overall, but it does use up more of the oxygen in the water and can cause problems for fish over time, too.
Sometimes leaf fall or other items in the pond can block the filter from working properly. Check the filter for things like leaves and large pieces of debris that are blocking the water flow. If this is the case, simply clean it out and the filter will run normally again. To fix the problem and prevent future clogs of this type, you can install netting on top of the pond to catch large leaves and other debris so that it won't be pulled into the filter. Remove debris caught on the net regularly to keep it from decaying and breaking down in the water, leading to overgrowth of algae.
Algae sometimes occurs even when your garden pond filter is working correctly. A quick fix for this problem is to introduce plants that produce a lot of oxygen. This helps to compensate for the oxygen loss that occurs when debris in the water breaks down, which allows for algae growth.
Sand filters can clog up for different reasons. Too much debris is the obvious one, but sometimes very little debris can cause problems if the filter isn't maintained or prepared properly. If your sand filter is clogging or plugging up, it could be the amount of sand or the build-up of sediment in the sand that's causing the problem.
Check the Manufacturer's Recommendations
The filter will come with instructions to tell you how much sand it should contain for optimum performance. This is usually around half-full. If you have too little sand, it won't filter properly. But if you have too much sand the filter can easily plug up and stop running.
With a sand garden pond filter, you want to backwash it—a process that pushes water back through the sand to clean the sediment away—regularly, about once a week for best results. If you don't do this often enough, sediment builds up in the sand and will cause the filter to clog. If you're following this process and still having problems with a clogging filter or a filter that simply isn't working properly, then it may be the water pressure. It's necessary to backwash the garden pond filter with enough force to remove the built-up sediment. If your water pressure is low, you might opt for a different type of filter to prevent clogging problems that can occur with sediment and sand.