My son have a 65g right now, its a tall tank, he have 3 sen and 2 albino, i might add some more, im looking for a retro, moke, polli, palmas & del. you can have 6 polys in your tank since they will be still growing, if you put them in a big tank while they are small they might have a hard time locating food. Its better to grow them first.Only a 60 gallon now but the plan is to upgrade to a 300 (240 at least) by the time summer rules around. I always planned to add more poly's I just thought 2 was plenty for the 60 gallon even though they're juvies. I like to keep my tanks understocked