ok so im nowhere near a 250... i have a 90 fw
planted... i run a single Eheim classic 2217...
that being said.. there have been several builds on this forum in the order of 180+Gal
... 300G the largest ive seen here...
after asking 1,000,000 questions and watching these builds.. if I were going to go as large as 250 and up... i would run multiple canisters..
1. you can never have too much filtration
2. you can alternate cleanings... if you run 2 canisters, you can clean one during week 1 and the second during week 2 etc... i believe mfdrookie516 does this on his tank...
if you can afford 2 fx5.... i would say GO MAN GO!!