Sorry to hear that your nitrates spiked.
Although some adult pods may be living in the junk in the bottom of such a container, unless you have a strainer (e.g., 93 microns), I wouldn't pour that into my system.
In the future, you should be able to see pods swimming in the water column and/or on the surface of the container crawling around. By looking at a bright light through the side of the container, you should be able see them.