I beleive a 75g is perfect for 4 adult discus....In my city, there's a breeder I know that's been dealing with Discus since the 70's....ALL of his breeder tanks are bare to the glass with the exception of a single brick....These breeders are 30g TALL tanks....Just one pair each, nothing more.....Most of his pairs go for $200-500, some $1000+.....So he's had some for many years making babies in the same 30g.....Please read upon these fish, I heard that their water perameters have to be tip top shape.....But, yeah, that 75 you have in mind will be just fine for 4 Discus.....Post pix....Bud_Man_Jr;550670; said:ok i will have a ac 110 on it.then later ill try to convince the parents into a 75 or ill save up from baby sitting.then i can get a few more