I think my fish are spoiled now.. as I can't imagine anything in the 2'+ range now that I watch them in anything less then 500+ gallons. I would think with that footprint a nice pair of larger cichlid would look striking and have room for some nice hardscapeing. imo a 4'x4' footprint isn't going to be sufficient for even the smaller rays for life but could last a long time for say a hystrix/retic (idk much about the sw rays but anything that nose to tail that is going to reach 24"+ imo is going to be too big) arrowana will also eventually outgrow it ect... When I got my 120 and moved my growing fish into it... I made a realization.. I really was going to need to hit the 500-1k mark if I wanted to keep my fish. Until we did set-up our pool I was skeptical they would "need" that much room... But they fully utilize the 1k pool. And my fish aren't as active or energetic as arrowana's .
Most of us wouldn't keep a 12"+ fish in a 75 gallon tank... take a 24" fish and do the math... 48"x 96" would be a min.. As a lot of fish grow I think a lot of people forget to follow the "basics principles" not that the formula is 100% accurate but its a good place to start... with a fish like an Afro that is almost constantly swimming I would expect them to need more space.
imo the 4'x4' is def a good start and will likely give you a few years but in the end you're likely going to want/need to upgrade for the long-term health of the fish. could they live for life in it? probably, we've all seen pictures of the Pacu and RTC's in 180's for 15yrs ect... people will argue why or how these fish stay that small.. but when the corpses are dissected the organs are enlarged and spines are twisted, severe health issues are shown. Not always, but often enough. Makes me want to ere in the side of more is.. well more.
I also found within' reason... get the fish you want, knowing you will need to upgrade. why? because your invested in the fishes well-being long-term.. you will spend infinatly more careing for/housing a fish then you will w/ the initial cost/investment. within' reason.. if you could never afford to house/keep an ariapiama... don't go buy one.. But if your "not sure" either wait and make a choice, don't just fill the tank with whatever looks cool at the time. I use to get crap for keeping some of my fish as juvies in small grow out tanks... now my set-ups include more gallons then the haters have. Know what you are, and are not capable/willing to invest into this hobby/your pets. If you "Know" your going to upgrade then I say go for it.... if like you seem to be leaned don't intend too.. we're here to make sure you don't have to re-home a valued pet because you don't have more space then it will realistically need. ( and of course to learn from everyone else as well, I've learned oodles more then I ever thought I would since joining this forum)
Also keep in mind if you've never done salt before... the cost of salt to do water changes...sw is much more expensive done right then fw.
