Need Blood Parrot Advice

[Nazasaki]

So after a hiatus in the cichlid keeping hobby I'm back with three juvenile blood parrots. They are temporarily housed in a 29 gallon and I'm going out on a shopping adventure today to pick up a new 55. They are staring to become aggressive towards one another in the 29 despite only being 3 inches big so its time for an upgrade. Ive had them over a week. I kept these fish many years ago when I was still a newbie to the hobby. So a few questions:
1) Are individual hiding spots necessary? For example, one terracotta pot per fish. I've heard that hiding spots are a must, and I have also heard they they just encourage bickering.
2) I have a group of three. No clue on the sex. Should I get a 4th so no one is singled out? Or just leave it as is. I'm at 102% stocking with the 3 and I'd like to keep it that way unless you guys suggest otherwise.
3) How can I determine the sex without venting? Or doesn't it really matter with a group?

Years ago I had 4 of these guys in a 55. I bought all of them at about 5 inches or so off of Craigslist. They never fought or bickered like these three. Hopefully the new tank and increased space will calm them down.

 

[Ihsnshaik]

Every fish has their own personality and as for sex cannot determine just by looking at them. Parrots are harmless they're deformed mouth makes them useless really in a battle.

I would put one pot and let the dominant one take over so there will be a pecking order

 

[Nazasaki]

Just from their interactions in this tank one parrot has taken over a piece of driftwood with anubias. he/she dug out a cave in the substrate underneath it and chases everyone away. I'm pretty sure that one has already claimed that it is dominant.

 

[ehh]

I wouldn't add a fourth. I think a 55 gallon is too small for four blood parrot down the road. I know there is some size variance in blood parrots but I've seen a couple softball sized blood parrots.

The only to sex them is to vent them unless their tubes are exposed.

 

[Nazasaki]

So do you guys think that despite the current fighting all three would be okay in the 55. I like the look of odd numbers anyway. I think the fighting in the 29 is due to space restrictions and that they will be much much happier once I get them into the 55.