So, Fork and Socket have moved to their very own, brand new 70l (tank 4 including my planted bowl - MTS has struck). There is a system of holes and caves for Socket to hide, plus water sprite and planted plants for hiding too. It is working well.
They had produced eggs in the breeder tank (3rd brood so far) but I left them behind and the filter has dealt with them.
This has left loads of space for the peacock gudgeons who are making full use of it. Since I removed the heater and its vents Hector has been despondent, but now he has adopted a new cave. None of the females are interested though. I'd like to see how he responds to fatherhood as if he isn't too aggressive I may add some tetras, but AqAdvisor doesn't recommend that if the male peacock gets too aggressive and territorial.
Two of the females, Florence and ZsaZsa, keep sparring but no harm done.
Interestingly, the water spangles are all pale or yellowing and I suspect the lighting is to blame. Maybe they are being bleached or scorched by it?