We have snails, worms, mayfly type insects, even woodlice living in and on our filters its nothing to worry about as @Tula was telling you it proves your filters are mature and capable of hosting differing life forms thats all .Thanks everyone for your responses. Glad the black algae is nothing to worry about. I was just cleaning my filters and I saw a little worm in the filter pad, is that normal or is that considered some kind of parasite? ? And also when I cleaned the second pump there were a few tiny snails is that another thing thats normal or something else to worry about?? I'm not to knowledgeable about this kind of stuff. I've been very lucky for the past 5 years I have never had any problems until this year when my fish started to die. Now I find myself questioning everything that seems a little odd to me. Guess I have alot to learn yet!! I knew I didn't know everything but I thought I was a little more knowledgeable than I am!! LOL
Dave