Strange Live Filterfeeding Culture Growin In Tank

[AQUANUTS]

JUST curious as ive had anew tank setup in my living room to house my 30"redtail and 3 26" pangasus catc and 2 30" arrowana tank size is 80"long 47"wide 32" deep have had it runing now for ten weeks but have noticed these small wormlike fiterfeedin culture in the one corner of my tank i only feed pellets and trout and once a month fresh prawns without there heads on so im stumped where they have come from any ideas as im stumped

 

[nukeonekitty]

Put this in beginners questions to get a better response.