125 gallon

Not planning on doing this anytime soon but I would love to in a few years. If you had a 125 gallon tank with say maybe 30 corys a few snails and maybe some otos, how many girls could you keep in such a huge tank? I don't know if it would make a difference but if I were to have a tank that large...

I got really lucky and stumbled across a really good deal on a Rena XP3 canister filter -- $70, the guy just wants to get rid of it. I'll be making sure it's in working order before I drop the cash for it. My only problem is this dilemma; it's rated for up to 125 gallons, but I only have a 70...