Several different groups of pond bacteria include photosynthetic, heterotrophs, sulfate reducers and methanogens. Photosynthetics contain chlorophyll and make food by using sunlight for photosynthesis. Heterotrophs live off of decaying matter. Sulfate reducers live in sediments, breathing sulfate instead of oxygen. Methanogens live on the bottom, producing methane or swamp gas. Most pond bacteria can only be seen through a microscope; large clusters can be seen as a scum or algae.
Aerobic vs. Anaerobic
Pond chemical companies offer mixtures of good bacteria to treat your pond. Good bacteria (aerobic) break down organic waste such as dead food and vegetation. Bad bacteria (anaerobic) produce odors and poor water quality.
Fossilized diatoms are used in toothpastes and filters. Up to 10,000 species of diatoms exist. Elongated diatoms move around and the round ones do not. Many pond bacteria can live on the surface of moist soil as well as in water.
If you are concerned about odor or scum on your pond, take a sample to your local agricultural center or state extension office for analysis.
According to safewater.org, avoid drinking from a pond as some bacteria like E. coli can cause illness. Water may be contaminated with this bacteria if you have farm animals using or living near the pond, or from wild animals dropping contaminated feces in or near the water.