Once the pecking order is established, just like any other SD the more the better, 3 or less seems to have more aggro IME with SD, especially if M to F ratio is 2M 1FDang, that's a lot of flow. lol But hey they look good so it's obviously no sweat for them. Not surprising as they are rheophilic as you and I have said. How's aggression between them? Mine can be combative at times, possibly because I only have three, and is another consideration in me getting more.
Either then that my specimens seem happy, eat well and cope well with each other and sub Sp. Of my other SD.