300 should be a good size for life for your Jardini. They can grow to about 2 feet long but a little smaller is more common. Whether or not it will share the tank, is up to your Jar. If it's not killing things in a measly 60 gallon and is already 14", I'd say you've got a good shot at tankmates in the 300. The "snap" can still happen later, or maybe yours is just a mild one. I would get the upgrade ASAP, they are quick growers and yours is already busting the seams on that 60.hes about 13-14" right now and in a looking very small 60 gal with the previously mentioned tankmates. theres the occasional chase but no biting and nothing too physical. im kinda new to jardinis and from a previous thread i was told that a 300 would suit it for life, but im not exaclty 100% on how big i can expect him to get