A mechanical problem at one of the National Zoo's pools on Monday may have led to the deaths of 11 stingrays and three other freshwater fish.
Tests showed that water from the pool showed low levels of dissolved oxygen, meaning the deaths could have been the result of a mechanical issue instead of a biological problem.
The first fish found dead was an arowana, which has a bony head and elongated body covered by large, heavy scales.
After it was found at 7 a.m. the zoo said it immediately took water samples and started refreshing the water from a reservoir pool. By 10:15 the water was back to an acceptable level.
In all, 11 stingrays and at least two arowanas died. Seven stingrays, three discus fish, boulengerella and a large school of guppies survived.