I have fish in it, only 8, 3" goldfish. In order to filter the dead
algae the UV would produce I set up a temporary filter thats basically
a 5 gallon bucket stuffed with quilt batting, I have not HAD to clean
it out yet. I have cleaned it, but it was still flowing water through
it so....It did have some brownish/gray muck stuck to it, Im assuming
this was dead algae.