I think that "monster" is a powerful word, the first time I saw this web site I saw the 50,000 gal tank, so I thought most of the guys on the forum had a pool for their fish...at least 5,000 gal tank....and I thought that because of the word "monster"....right now when I hear monster I see 60cm long fish minimum.....when I started I thought that a 60 gal tank was huge because I saw 25cm fish on that tank so the fish looks bigger.....
I have a 765 gal tank and sometimes I think is a monster tank and sometimes I really dont think so...and thats because I think a real monster fish should have way more space... but on the other hand if you have a 20,000 gal tank the fish will look smaller .....I remember my 60cm pacu on a 150 gal looked huge....
now in my tank looks not so big.....and if I put it on the 50,000 gal will look way smaller...
Last month I went to Belize for scuba diving and I saw a lot of goliath groupers, tarpons and barracudas (more than one meter each one)....and I thought that if I want to keep that size of fish ...then I will need a big pool....those are the real monsters...