I had a problem with red slime.
Suggestions on how to fix problem
1. Cut down on lighting. I cut back to 7-8 hours which helped alot.
2. Do more frequent water changes.
3. Watch overfeeding of your fish.
4. Red slim is bacterial and a UV light kills parasites, but I changed bulb and it helped for some reason but I don't understand why.
5. Added snails and they love to eat the red slime.
My tank is now free of red slime which is probably a combination of all of the above reasons.