+1. a 75 gallon is fine for one tank but not two and for sure not three. The fish will fight constantly and disrupt your tank. Royal Blue is also probably a bit too large for your tank. I'd look at the fish Mike suggested or maybe a yellow or scopas tangStang Man said:For a 75 that is not a good choice, to small of a tank to house three of them in that size tank. It can lead to a house full of fighters due to the species and region that they come from, these type species need a lot of room as they grow so please take into consideration of your choices for such size tank. Also can you give use a full desription of how you maintain and also equipment and all that you have in your tank currently?