Okay, another "what type of dishwasher soap do I use" question. Sorry.

I have a 3 year old Frigidaire, manual says it has a "self cleaning filter." I use Seventh Generation pods, and run a Lemi Shine pack once a month. During a recent visit from the plumber for another issue, I asked if that filter was a real thing. He smiled and fished the filter out. It was coated in a few inches on white sludge. Is that the plastic pod coating? Please tell me the best soap to use that causes the least wear and tear. Thanks much!