Pond Filtration Through Mussel Strength

Our pond is a large system: about 3,500 gallons, 50 fish, and 5 ducks. There is one large pond, connected to 2 kiddie pools, and 2 larger prefabricated ponds. There is no doubt that we did it backwards by starting with the ducks and building the pond later. Initially, they had use of the kiddie pools and we emptied them on a regular basis. In some ways I miss that as it was much easier to maintain, but we have loftier goals of nitrogen rich water feeding plants and veggies. Our goal is a mini ecosystem that allows for dirty duck water to presto changeo into food, shade foliage, and clean water cycled back into the system.

Unfortunately, the biggest hurdle to that is the ducks. Our first plan was to keep them out of the upper ponds and the kiddie pools as those would be for said plants. They are greedy and continued to test our insufficient fence, finding all the weak spots. They love that they can reach the bottom of the bottom of the preformed ponds and the kiddie pools make for an easy snack and a safe place to lay their eggs. With the heat of the summer and other obligations we ended up taking the fence down and letting the fight go, for now.

http://www.phillywatersheds.org/category/blog-tags/ttf

The fence will come back and the plants will be replanted. Yet, another idea has taken hold as we consider how best to keep the ponds from becoming nothing more than algae. What else could offer superior filtration power? Where could we find such strength, such mussel? Hee hee. Yup, bivalve filtration is incredible for eliminating plankton (i.e. algae) from the water. In fact, the concern, as stated in the article linked to in the previous sentence, is removing too much of the plankton thereby disrupting an important food source for the fish. In large scale operations that are placed in open systems great care must be taken to avoid invasive species that can wreak havoc on the balance of the native ecosystem. The picture above is from a watershed festival hosted by the Philadelphia Watershed Office showing that 'an adult mussel can filter up to 20 gallons of water per day'. We would certainly need a number of mussels to make a dent in our system, but they will be a piece of the larger, biological filtration system.

We have a local, backyard fish supplier who stocks mussels (as well as many other really neat varieties of fish and plants). We have not yet invested in any mussels or other filter feeders, but this is looking to be an essential part of our longterm plan. The ducks will leave the mussels alone, but introducing arthropods (shrimp or crawfish) to the upper ponds would be a nifty treat for the ducks, not so much for the health of the system or my wallet.

There are a number of articles discussing the impact of molluscs on water quality.  I suggest checking out the following articles for some interesting studies and information:

• Measurement of Filtration Rates by Infaunal Bivalvesin a Recirculating Flume conducted through the USGS and published in the early 90's. It's a heavy read and marine focused, but interesting. 
• Approaches for Evaluating the Effects of Bivalve Filter Feeding on Nutrient Dynamics inPuget Sound, Washington conducted through the USGS and published in 2013. Also a heavy read, but interesting as well.  
• On Measurement of Filtration Rates in Bivalves — The Stony Road to Reliable Data: conducted by the Research Center for Aquatic Biology  and published in 2001.

In the coming months we hope to incorporate 25-50 mussels into the system and get our plants up and running to clear our water and improve our mini-ecosystem.

Endangered Species Coalition