Probably filamentous algae.
There are some options:
- It can be raked from the pond manually with a LOT of time and labor
- Stocking anywhere from 5 to 35 lbs per acre of tilapia at least 6 to 8 inches in length can take care of it within a year or two depending on how many you stock and assuming the bass don't eat too many of them
- A copper-based herbicide like Cutrine can knock it back
- Reducing or stopping any fertilization or feeding programs can slow it down
- An aquatic dye applied next spring when the water gets into the 50's can prevent some growth next season, but it won't completely stop it
If you end up going with herbicide, send a water sample to a county extension office and have them check the alkalinity. If the alkalinity is below 20 mg/L, any copper treatment is very risky. If the alkalinity is good (above 20 mg/L) only treat 1/4 to 1/3 of the pond at a time to reduce the risk of oxygen depletion and follow the product label instructions. Best management usually comes from a combination of the above recommendations. The root of the problem is usually the water being too clear and/or the pond being too shallow and/or too many nutrients accumulating in the pond. Identify the primary problem (for example, excessive nutrient input) and solve it so that you won't spend as much time, effort and money each year on treating the symptoms (for example, dense filamentous algae growth).