Wow, I'm surprised that this thread is still going.
Just to clarify a few things .......
While I have always agreed that a single Mbu does not require a 1,000 gallon tank, some of the comments in this discussion defy logic, such as a 24" fish with a massive girth that eats like a horse, can get by on very VERY minimal water changes when housed in a 180 gallon tank. That's just plain ignorant, and totally absurd.
Most of the waste produced by a fish isn't in a solid form that you can see with the naked eye, and bio-load does not just equate to how much
crap is produced by a fish. One of the leading causes of cataracts in aquarium fish is bacterial based, often caused from poor water quality, so that certainly leaves your comment about this fishes living conditions having no effect on its health & overall condition open for debate. The reality is you have no idea whether the conditions that you have kept that fish in have been the direct cause of any health issues. I'm not saying that it has, I'm just sayin ......
From a previous post of mine in this thread;
Your logic of thinking that modern filtration (canisters & HOB filters) is going to add a big plus to the equation also shows how little you understand about water quality, and bio load.
You still seem to be under the misguided notion that massive filtration equates to pristine water quality ..... it doesn't! Pristine water quality comes from massive water export & import, NOT massive filtration.
The link that you posted of the arrowana community tank was from a link that I supplied, but with regards to bio-load that set up is nothing like yours. That tank is owned by a friend of mine who has all of his large comm tanks, including that one, on an auto drip system which allows him to dial up or down the water changes depending on the tanks bio-load. That tank that you linked to was at that time receiving 100+ gallons of fresh water on a
daily basis, in order to keep the nitrate levels below 10ppm, and in order to keep
all water parameters at a constant level. His fishroom has between 400-500 gallons of fresh water coming in every single day. That's a huge difference from someone doing
minimal water changes, as though that's something to be boasting about. This person has learned from hands on experience with massive fish and massive appetites (and past mistakes) as to how water quality can effect a fishes growth & overall health in a positive, and/or negative manner.
I have absolutely no problem with those that feel they can supply an adult Mbu healthy long term conditions in tanks under 1,000 gallons, but to argue that this can be done with an adult mbu in a 180 gallon tank, with minimal water changes, is just plain piss poor advice.
I only came back to this discussion & post this in the hopes that someone that's new to this species doesn't get any ideas that this type of set up is in any way ideal for the fish, because it won't be.
Carry on ........