Frontosas and yellow labs are from 2 different lakes. try to find another tang species to mix with your frontosas. Not a Tang guy myself but I am sure other tang keepers can help you out. Best of luck. Frontrosas rock I just don't have a big enough tank to keep them yet...lol
I wouldn't recommend any other mbuna, but yellow labs are so calm that it could possibly work. Obviously you are taking a risk, because the fronts could eat the yellow labs at any time, if they chose to do so. You have the best chance if you introduce small fronts to adult yellow labs, and I'd say you have virtually no chance if you put yellow lab fry in a tank with adult fronts. Anything in between is hit and miss, but it could work - at least for some time.
Regarding the leleupi, I am keeping them with my fronts in a 240G, and the mix has worked well now for about 6 years. In a 6' tank like a 180G I would probably try the yellow labs rather than the leleupi. A breeding pair of leleupi can get fairly aggressive, and defend a rather large territory, which would take valuable real estate away from your fronts. Yellow labs generally don't defend a territory in that way.
Leluepi and Electric Yellows are about the same size, so either one if too small will potentially become a meal.
yes, Leluepi when breeding will be more aggressive than Labidochromis, so the EY's are a better fit.
The difference in lakes does not matter, as F100 Labs, and F2 Frontosa have been raised in water nothing like what they came from.
Another option would be Albino Eureka Red Peacocks, and Placidochromis phenochilus "white lips"
Thanks so much guys for your input.. *** dropped the EY's into the tankI purchased 5 but from the looks of things one of them may not make it but the others seem to be pretty healthy. I put the EYs in forst with hopes to give them a fair chance before the BIg guys get introduceed to the tank