Well,jds are slow growers,compared to Oscars,Midas,Dovii,ect.my Jd is around the 6 in half inch mark close to 7,but I have the jd in the 125 gallons,if you keep looking around on craigslist or even petco wants to get rid of their old tanks,which go on clearance usually,you can easily get a 75 gallon with stand for 150 or below.that would be more room for the jds,since the width is 18 inches.I think in my opinion width is more important and at least 5ft or above for length.As for height,I guess it plays a roll too,but most cichlids are bottom and middle fishes