Goodness, so much fuss over little copepods.
Kveeti’s photo appears to be a harpacticoid copepod. This Order is more or less a bethnic omnivore on lower trophic organisms and algae.
Blinky; cyclopoid copepods are a more pronounced teardrop shape; that may be your critter. In an aquarium they’re mostly predatory on rotifers and ciliates. In the wild they’ll attack anything their size. Cyclopoids aren’t detrivores, but detritus in a tank will support the organisms that these copepods feed on. Cleaning up the tank a bit should help. My leaf litter tanks (fishless) have strong copepod populations.
As an aside, newborn fish fry can be attacked by cyclopoid copepods (or cyclops) and there are some that are parasitic on fish. I would rule them out unless you actually see them on the fish or see tissue damage.
Beeker; that ‘silverfish’ you have and ‘loss of snails may be predatory insect larvae (mayfly, damselfly,etc…). I use snails and scuds as a prime source of prey for aquatic insects.
Linny; are they crawling or hopping? Copepods don’t crawl, so you can rule them out. Ostracods and water mites crawl.
I’d have to say that over the years maybe a 3rd of the plant orders I received have had copepods brought in with them.
Tom
), but the basic shape is the same. There aren't many, I can see maybe 50 or so on the glass. 