I have to say that Red Slime Remover does work...but keep an eye on your pH, read the fine print on the box. It cured my problem, but killed at least 3 fish cause I wasnt paying attention. My ph dropped to like 7.8 or lower; took me at least a week to get it back to normal. If you must use a chemical, test your params daily and be ready to do a significant water change. I have read that people have used it and did water change like a day or 2 after treatment with no probs, but I dont recommend it.
You obviously have a short light period, but is it getting any direct/indirect sunlight? Often that can cause an outbreak. We're battling the slime right now and I think that is part of our prob, so I've been gradually changing our sched. and lessening (is that a word :notsure: ) feedings and, of course, more frequent water changes. We definitely have seen a difference. Also, as mentioned before, water circulation. In an attempt to test this theory, I repositioned 1 of the PH toward the substrate and have seen a noticeable diff in the area where there is more flow. Looking into getting another PH or 2 soon. HTH.