As a follow up to this, on Sunday we added some more fish; a pair of Bolivian Rams and a pair of Butterfly Cichlid Rams. I asked the guy in the shop if these would be OK together and he said if they were added at the same time they should be fine.

Fascinated by their behaviour now. The Bolivians stay mostly at one end and the Butterflies at the other. Yesterday they were all on a real mad-one taking it in turns chasing the others around the tank, but have settled down today. None of the other fish seem bothered by them, apart from the Harlequins - and they're just shoaling more, which is fun to watch.

So, what we have now all seem to be middle/bottom dwellers and I'm wondering how we'd get on adding 1 or 2 top-dwellers, like Angelfish. I know they can be aggressive towards each other and smaller fish, but I thought if we got small ones, they might be OK.

Current stock:

10 x Harlequin Rasboaras

10 x Neon Tetras

4 x Black Corydoras

2 x Bristlenose Placs

2 x Bolivian Rams

2 x Butterfly Rams

Tank is 180l - 101x41cm x 50cm deep

As always, I'd appreciate any feedback/advice.