i gave you plenty of advice
get a tank that is min size of 72inch long x 30inch wide x 24inch deep with double the amount of filteration as you think is enought make sure your heaters have heater gaurds on them do big water changes of 25% min every week
dont buy any rays until you have had the above size tank set up for at least 6 months
when you are ready to buy a ray make sure you see it feeding in the shop before you pay any money as 80% of ray problems are i cant get my new ray feeding
rays can be kept with other types of fish arowana are a very good tank mate for a ray just stay away from jardini if you live in canada then buy an asian green they are a good starter arowana
a good way to see how big a motoro gets is go outside and look at the wheel on a car with the tyre thats how big a motoro will get female upto a 24inch disk and males 16-18inch disk and they grow that big fast if you buy a 8inch disk motoro expect it to get to 14inch + in about 1yr
anything else you need to know just ask