What about barley straw?

Barely straw is a great way to add healthy bacteria, naturally, to a pond.

It can take from 4 to 6 weeks to see results from barley straw, but patience pays off!  Barely straw can last the whole season!  As it begins to decompose, it creates and enzyme that helps to reduce algae. Follow the instructions to add the right amount.

When using barely straw, it is imperative that it is organic.  Straw that may have been treated with pesticides could kill the plant life and even the fish in the pond.