This Thread is very compelling. I have two spawning pairs of discus in my tank. I had to upgrade to a larger tank and when I did that the color of substrate that I needed and it was a lighter color to match The Hardscape had to be an African cichlid substrate. The one pair spawns about once a week the other pair about once every month or so. Before the substrate change I had 90% success on getting Wiggler's. After the substrate change my hardness even with water changes is much higher and I get zero Wiggler's. I think this is my problem I don't know if anybody is still looking at this post. But there you go