First of all the op disagreed with the title of this thread and said Oscars don't need a big tank and a 55 will work.
In most cases it won't and the ones that it does work in are just prison sentences.
Secondly, if these people didn't ignore the advise of experienced keepers then a more realistic choice could be made.
Cichlids come in many shapes and sizes.
This is exactly what he said.
"For number 5, no, you don't need a huge tank. A 55 will work, but a 90 would be perfect for an oscar, no problem. You don't need a huge tank like he was saying"
Yeah 55 is generally to small, infact i wouldnt keep one in something less than a 120.
Dont you beautifully scape your tanks ? Fill them up with great looking natural decor ? How do you know that the space left over is sufficient for the fish ?
You know what they say about ass holes, everyone has one... this thread sure has allot too