I started off with 6, and then had 12 in a 180l.
They were definitely happier with higher numbers, and also when they have peaceful tankmates.
I put a single endler in the tank with them and their behaviour was considerably modified.
Mircorasboras, pygmy corys and otos on the other hand all made good tank mates.
I kept them in blackwater conditions (pure RO water) at a temp of 26deg.
Was quite a challenge keeping the tank stable at times.
They spawned once though, so it was all worth it
I've currently got 5 in a 15 gallonish tank, they look a lot happier then just the pair did
HOW did you get them to spawn? and did you see any difference in male and females?
I think 5 is a good number
I did not do anything specific to make them spawn, I think lots of plants and good water quality were probably the main factors. I will do a summary of what I did (and didn't do) here...
sexing:
I never noticed a difference between the males and females, but to be honest, I never looked that hard.
plants:
A lot of sites tell you to have lots of floating plants for cover. A choc gourami's definition of cover is that when you look straight down onto the tank from above they can not be seen. So, while floating plants were good, any large leaved plants (eg amazon swords and anubias) were also perfect for them to 'hide' under. While hiding they can be seen clearly from the front viewing pane of the tank
food:
Staple food was a mix of frozen fare (bloodworm, daphnia, brine shrimp, baby brine shrimp, cyclops)
and an army of dwarf shrimp (~200) for them to snack on, so they had a continuous supply of live food.
Live daphnia occasionally.
water chemistry:
The tank was run on 100% RO. TDS going in was about 10ppm. I used to water change enough to keep the Tank around 100ppm tds. They will tolerate higher TDS (eg London tap water of ~350ppm TDS) without any issue if acclimatised slowly (ideally upon importing and slowly over a number of days\weeks by your LFS).
I spent a long time tinkering with peat, indian almond leaves and alder cones in varying combinations. After several months I slowly stopped adding these as I do not think they made any real difference.
I got fed up with the hard work in balancing the tank between blackwater and planted tank so started to phase in some (350ppm) tap water at each water change and some extra ferts. It was a few weeks into this that they spawned. I do not think it was the increased TDS that caused the spawning, but the increased water quality that was a result of the increased plant health.
Water temp 26deg. They do not tolerate lower temperatures. I lost all the fish when my central heating was turned off during a winter holiday and the temp in the tank dropped to about 15deg where the heater couldn't keep up.
Coloration:
They are beautiful to look at, when healthy the chocolate is very dark, and the bands go a very bright gold colour. Mine took about 3 months to colour up completely. When stressed the colours go blotchy. When ready to breed the gold and chocolate was complemented with red tinges on the body and fins.
Behaviour:
They continously circled each other. Sometimes quite subtly (slight body twists while a couple of feet away form each other). This never ceased to captivate me, it was as if life was one long dance class! There was a definite pecking order and I got a sense they were all working as one unit on a number of occasions. For example, when one had fry in her mouth all the others were like a swat team circling round her protecting her at all times.
As well as change in colour they exhibit different behaviour when stressed. They will lie on their side and flutter like a leaf. If you have leaf litter in the tank (beech is my leaf litter of choice as it does not affect the water parameters and takes 2-3 months before it starts to decompose significantly) it is very hard to spot the fish.
Stock:
It is very important that the LFS takes good care of these fish prior to your purchase.
If your LFS chucks them straight into tap water upon import then I do not like your chances of keeping them alive more than a few months after purchase.
I recently saw some healthy specimens in a local LFS that I trust, so may dive in again with these fish...
I saw there is an anabantid inventory thread, so will post this info there as well (with some pics).