K leaves are kepatang leaves. They soften the water. Reds do better in softer water but there are several ways to achieve the same result. Just be careful you don't create an unstable environment.
Some people use tanning lights and start with three hours on, aside from normal tank lighting but concurrently. The next day they increase the tanning lights to 6 hours. The next day increase to 9, and so on. There's no real science behind this but the idea is to acclimate the fish to the bright light. A lot of guys just leave their normal tank lights on 24 hour a day for a week at a time and they see results. All tanning really does is darken the fish, just like you tan under the sun. It's essentially the opposite of white tank treatment.
One more thing. If you tan your aro, you can expect the eyes to become cloudy. Some use that as an marker to stop tanning. Again, the schedules are different for when to start again.
