Sometimes water conditioners can create a slimy substance. Have you switched conditioners recently?
I've seen a lot of posts similar to this with conditioners that contain aloe vera.
If it's stringy and white, it could be poo..I believe stringy and white poop signals internal parasites. That will require treatment.
A picture would be helpful.
Also..in anything unfiltered(actually...even if it has a filter), and under 2G, I'd suggest 100% changes every other day. 100% changes are the only way to completely remove ammonia.
With your next water change, check your dosage of water condtioner..if you're adding too much it can create a build up. Also check and see if there is aloe vera in it..(if there is, I'd buy a different conditioner next time).
To my knowledge, fish don't 'shed' their slimecoat like a dog sheds their fur.