haha it started a few weeks ago... with the guy that owns the house i live in is an avid saltwater guy.... he gave me a 10 gallon with a undergravel filter and a heater.. then 200 dollar later.... the tank was ready for 6 dollars worth of fish
anyways normal fish are fun but stingrays truley appeal to me... i want one really bad.. space is more of an issue then cost .....
you have access to a 90 gallon for free!? I'd get that one and try something different for a while till eventually you can get a huge tank for the rays. there are tons of options for a 90 gallon.
I think you are making the right choice concerning the rays.
im pretty sure thats the one that will fit in smaller tanks 180 seemed a bit exsessive to me... but this is making more sense now... but my tank still needs to go back and replaced with something bigger... just waiting on the text about the 90 gallon ....
back to your filter choice i would go with a canister i have a fluval 405 on my 55 gal and it does just fine. you could always throw the whisper on as well for a little bit more filtration. also rays take a LOT of work and are not easy to keep. if i were to setup another tank it would be a puffer tank because they are so interesting.