I bought my 40 gallon tank frommy uncle a year or so back, and I just punched in the dimensions into an online converter that tells the gallonage, and it turns out the 40 is really a 47. I assume that my octopus will not miss the 3 gallons smaller than recommended for a bimac Well, which should I get? A bimac, or a mercatoris? I already have cycled sand, live rock, and water to put into the 40 (it's RO), so it will not need any cycling time. I have a filter rated for 125 gallons, and then a power filter rated for 80 gallons. I'm leaning towards the bimac (duh...) just because they aren't nocturnal, and are more interactive. I'll also have fun giving him enrichments, etc. Why did I even post this question again? Lol. Well, I guess i'm more of letting you know that i'm getting a bimac instead. I'll have to PM marinebio_guy huh?