should there be squirming things in filter

[agnitoood1]

as I swished about the filter media in a sink of dechlorinated water and then watched I saw moving things. so i took out my microscope and found lots of things in there that are moving around.
I treated for internal parasites in my pleco for 2 wks in a qt tank and dropper feeding him his food. he got better.

my real question is are there some little critters that are ok to be in your tank/filter media? any others that i should be real concerned with if seen?
and I think I saw more than my stomache could handle at times.

these little critters here seem to be the only ones left. they look like white swimmin specks when on the black rock or driftwood
www.microscope-microscope.org/gallery/Mark-Simmons/pages/ostracod.htm


75 gal
2 -2" oscars
1 - 12" pleco
live plants
fluvial 304 & hob filter

thanks for any more insight as to these critters.

 

[Devilishturtles]

Probably some sort of planaria or copepods. Most evolve from an over abundance of nutrients and bacteria in your tank. Usually nothing to worry about, but can become unsightly.

How often do you do a water change? When was the last time you did one or changed the filter media?