I noticed this floating suff in my filter tonight... It looked real gross through the plastic, and its been a little over 3 weeks since I changed my filter... So I replaceed it. What I found was kind of gross. It looked like dark black slimy substance.. maybe even a deep purple. I went downstairs again to check about an hour or so after I replced... I can see the "stuff" floating around the filter housing again. This is so sudden... I changed my filter last on Thanksgiving and maybe all I had was a rusting issue, NOw this... I fear for my family's safety and I don't know who to call... Im afraid if I call a plumber, He'll try to sell me something I may not need. I have no problem getting a UV light if that's what I need.. but I do not want to buy one out of fear without being assured that is what I need... Any one know what tis slimy substance may be??
Ps... It didn't clog up the filter though

Are you using a white filter cartridge for sediment only or a black one for taste and odor [chemicals]? Are you on a well? Are you on municiple water? If you are on municiple water then set up a pre filter for sediment only. Let the chlorine stay in the water until it reaches the next filter which can be for taste and odor.
Be glad you got the filter, you now see what is in your water. Most municipalities have a place for free water testing. Try that

It's a well... after reading online.. I believe it may be iron or sulfer bacteria. I checked inside my toiklet tank and there is a dark green/black slime buiild up... so now what?? Do I need a UV light??

You may have to chlorinate your water then filter the chlorine out. For the toilet you can put a chlorine tablet in there but you are drinking this water. I would chlorinate it and not filter it after the chlorine so I could chlorinate my pipes to avoid a repipe. Definitely use the sediment filter and have the water tested.

I noticed that you said you could see the stuff through your plastic filter. Are you describing a table top pitcher like a Brita or Pur filter? The whole house filters I have installed are not transparent.

Yes this a whole house filter... The casing is clear... I have bought the best kinds of filters that home depot sell for these filters... they supposedly take out the bad taste and odor as well as all the other crap.
Well, I was thinking I was going to install a uv light to kill the bacteria instead of using bleach in my well. I am still going to have my water tested though.