They would need at least a 40gal tank or bigger. The Bicolor angelfish can be very finicky and in my experience is not very hardy compared to many other commonly available dwarf angels like the flame and coral beauty angelfish for example.Dwarf angels are known prey items for many larger reef fishes. Which explains their inquisitive and alert behaviour. Placing these fish with larger predatory species should be avoided (ie: Groupers/Bass, Lionfish, Triggers). Correspondingly, smaller docile tankmates should be avoided. As they will tend to get chased around the tank regularly. Although many keepers have successfully housed Bicolour angels with smaller species, caution should still be considered. Dwarf angels are best introduced into communities last or close to it.