To be fair ray pups can been grown out in any tank to suit their size as long as you are prepared to upgrade at a later date
filtration has to be right yes but the use of expensive fx5's (not that good anyway) or huge sumps is not needed
all my ray tanks have a built in filter system at one end and all are driven by air (no power filters) old school filtration and its the best
only use korelia wave pumps for circulation
way to much info is given on rays needing massive filters etc etc and it just isnt true some keepers are way over the top with their expensive fish gadgets, filters, uv's etc all it is is showing off just how much cash you have spent
look at my tank i spent £K's setting up!!! bigheadedness i call it
many keepers in holland and the uk have actualy raised and bred rays in 6ft x 2ft x 2ft standard tanks
i would say 2.5ft wide is better but wouldnt go past the 3ft wide mark and 3ft tall is just daft 2ft is fine
a good mate has a leo male in a 5ft x 2ft x 2ft (pet ray) on his own! has an 15" disc and is happy as a pig in poop his filter is a normal pond filter box above the tank and is fed from a 1300ltrh pond pump at the back of the tank his water is drinkable lol
he has no uv, no fx5's, no sumps,
a good air pump is needed on all ray tanks mine have at least 3 big airstones in each
just remember if you are thinking of ray keeping start small pups and work to upgrade when ready as not all keepers can cope long term and it is a long term commitment keeping rays
so think long and hard befor taking the plunge