If I remember correctly swan mussels are used, the big quoted danger with them is the pollution associated with their decay when they die, I also seem to remember thay have odd breeding requirements involving one species of fish.I have an unintentionally introduced shell fish population in at least one of my ponds but they are half the size of my little finger nail and rather delicate, they would never contibute to filtration.


Do not use zebra mussels or any non native shell fish, zebra mussels are causing 'havoc' in Irish water ways and have definately contaminated Lough Erne and have been founnd in Lough Neagh, I think they are in the Shannon too.