I have an achillies, naso, hippo and purple in a 270g, they have all grown alot in the past year, I am very attached to all of them and hope I don't have to sell them. I have housed a sohal in a 150g and had to sell him because it just wasn't enough tank for him, he was very unhappy. I also think my achillies would be unhappy in anything much smaller than the 270g.