The ctenocephalus are super cool! I'm trying to get my hands on some gastro. cheni. As far as their "need" for high flow conditions, dude at brianstropicals.com has had great luck breeding sewellia lineolata in tanks with not much more than a sponge filter, and has also reported much greater survivability of the fry in these low flow conditions, so as long as their needs for high dissolved oxygen content is met, the flow issue is probably far less important than it's made out to be.