Hello to everyone! In one of my basins I occasionally dump a little water from filters. The bulk of the basin's contents is old tap water. A moment ago I discovered these critters (I posted here because I am pretty sure they have no vertebrae): Could anyone tell me what they are? They move slowly. The "body" is between abt. 0.4" and 0.8" long and that strange threadlike appendix is much longer. It is not very likely I will feed them to my fish, not even to my voracious (dwarf red) Blue Gularisses (aka Fundulopanchax sjoestedti, one of the 2 males male to be seen in the avatar). Would these animals eat my fish? They kind of make me worry.. Thanks in advance for any reaction!