After spending 2 years living alone, it's extremely unlikely they will get along. A 6ft tank is not very large - that being said, neither should be living in 3ft tanks, they are MUCH too small - and the male will likely just take over the 6ft tank and kill anything else. Assuming you actually have a male and female, you haven't said whether you know the sex of them or not. Either way, forcing a pair of adult flowerhorns into pairing is almost impossible, especially after living alone their whole lives and in a tank that is too small for a pair even at the best of times.
