yeah but i couldn't just go out and ask for 1 male and 3/4 females from just anyone could i? from what i have read they are hard to sex even at the best of times, males grow the hump but even older females develop a hump so even that method isn't precise. even if i got a group, and they lived happily, how would i know which was male and which was female? even if they bred, unless i watched them 24 hours a day id not know who was who would i? is it the females that hold the fry?
would 1 dominant male chase all of the other males away or do they tolerate each other?
i think i read that the dominant males would only chase off other males that challenge it and tolerating those less dominant males that just tag along so to speak, so in which case how would i then tell the sex's apart?
when i first filled up the tank it was ph 7.0 and was constant until i put in the wood and the almond leaves, to lower the ph for the rays, it went to a constant ph of 6.5, but when i decided to keep the tiger fish i had to bring it back up to 7.0 to have the b est of both worlds. all along whatever i set the ph at it stays constant which is a good thing right? so i can keep it at a constant ph of 7.0 as it is now, but i think if i higher it any more would be unsuitable for the rays.
if the fish (if and when i get them) are small (less than about 3") they will be grown on in a smaller tank first, in which case i could adjust the ph slowly, if i set it at around 8.0 and lower it to 7.0 over 6-8 months until they are big enough to go into the big tank, would tis be a better approach?
this is assuming they are being kept in a higher ph at the moment, this is irrelevant if the fish are already being kept around the 7.0 mark.
if they are small, and obviously an unknown sex, how many would you suggest i start with, to ensure i have a good mix, baring in mind i have plenty of space for them.
so ultimately, pre-hardness test, i am asking if it is possible to keep a group, happily!, in a ph of 7.0 (very stable), with a load of space, there will be rays in there, but im quite confident the rays wouldn't bother them and they wouldn't bother the rays, a tigerfish, which seems quite placid, the arowana which stays at the top really, and the characins which also stay at the top, oh and my fire eel that only comes out when you stick prawns in its face and the syno multipunctatus, which is wild caught and doing extremely well in the tank, if the water was really soft i doubt the syno would be doing too well!
what do you reckan?
/www.frontosa.com/ and your questions will more likely be better answered there, lots of good information and experienced keepers/breeders there 
