In my 30gal(35 gal system water),I have 3 fish.2 Pseudochromis spp.(dottybacks) and a mandarin.This system is nutrient poor and only gets small daily additions of flake and sometimes mysis.The mandarin only eats pods and has been with me over 2yrs.In hindsight,I wouldn't have put a mandarin in this system because they decimate the pod population and those(amphipods) are excellent grazers of turf algae.The 1 dottyback is very aggresive and is clearly dominant.My sunrise dottyback has coexisted with him but because he's submissive he doesn't have the bright colors like he used to.Probably will be taking the aggressive one out and moving the mandarin to my 40.
In my 40 gal(48 gal system water)i have 3 fish.A breeding pair of Tomato clowns(Amphiphiron frenatus) and a Radiant Wrasse(Haliochoeres iridis).
The clowns are very aggresive and nothing can enter near their territory(bottom left side of tank).Even when i have my hands in the tank,the big female bites me.The wrasse does coexist but if he ventures too far to the left side,the clowns quickly chase him off.I wont be adding any more fish to this system(maybe my mandarin) as i don't want any more bioload because the clowns receive saturation feeding everyday.