Well I can help you with what I would do to get your tank reset up. USE BLEACH for the tank, filter system, heater, etc. Bleach is a powerful disinfectant that will probably make your tank safe to use again.any help is appreciated. I have had an established aquarium with one electric blue african ciclid for over a year. a few weeks ago i added another and things were going good so i bought another (orange african ciclid). it did not fair well against the others and was huddeling a lot. 2 days later my original blue and my new orange were found dead. the next day the new blue was also dead. today i was doing a water change and planning on getting 2 oscars and start over then i saw THEM! small brown/black worms were in the water moving and on the glass. about 6 or so were in the water change waste water bucket when i dumped it out. i tried to google these critters but not finding much luck. i have never fed live only ciclid flakes. i don't think they are planaria as they are not white. did these worms kill my fish? are they harmful or just coincidental? i'm including a photo. i have not done a water change in quite some time 6 mo. or so. I feel terrible. i'm sure this probably could of been avoided and don't want it happening again. i am scared to put any fish into my tank now. sorry about the rambling. i guess i am looking for any info. please help. thanks, JASON. View attachment 23296
Throw away any filter media that you were using.
Gravel and Rocks I would dispense with too, Where Gloves while you are doing this as you never know the harmful bacteria and pathogens that are around in this aquarium.
Regular water changes are important.
I have seen red worms that act like parasites but I have not seen anything like what you have posted here.